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	$232.92	8.651%	$253.0699	$253.07	$253.05	$253.10
Purchase #2	$50.27	4.508%	$52.5362	$52.54	$52.55	$52.50
Purchase #3	$134.45	5.678%	$142.0841	$142.08	$142.10	$142.10
Purchase #4	$97.29	12.824%	$109.7665	$109.77	$109.75	$109.80
Purchase #5	$162.27	10.500%	$179.3084	$179.31	$179.30	$179.30
Purchase #6	$192.93	8.488%	$209.3059	$209.31	$209.30	$209.30
Purchase #7	$36.59	4.272%	$38.1531	$38.15	$38.15	$38.20
7 purchase totals =	$906.72		$984.2241	$984.23	$984.20	$984.30