Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$127.57	9.856%	$140.1433	$140.14	$140.15	$140.10
Purchase #2	$118.44	4.245%	$123.4678	$123.47	$123.45	$123.50
Purchase #3	$111.92	4.487%	$116.9419	$116.94	$116.95	$116.90
Purchase #4	$176.31	12.595%	$198.5162	$198.52	$198.50	$198.50
Purchase #5	$213.28	7.618%	$229.5277	$229.53	$229.55	$229.50
Purchase #6	$113.79	5.723%	$120.3022	$120.30	$120.30	$120.30
Purchase #7	$232.36	13.219%	$263.0757	$263.08	$263.10	$263.10
7 purchase totals =	$1,093.67		$1,191.9748	$1,191.98	$1,192.00	$1,191.90