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	$227.51	9.206%	$248.4546	$248.45	$248.45	$248.50
Purchase #2	$200.37	9.562%	$219.5294	$219.53	$219.55	$219.50
Purchase #3	$144.28	5.314%	$151.947	$151.95	$151.95	$151.90
Purchase #4	$115.41	3.241%	$119.1504	$119.15	$119.15	$119.20
Purchase #5	$171.76	6.143%	$182.3112	$182.31	$182.30	$182.30
Purchase #6	$198.28	10.146%	$218.3975	$218.40	$218.40	$218.40
Purchase #7	$53.67	10.473%	$59.2909	$59.29	$59.30	$59.30
7 purchase totals =	$1,111.28		$1,199.0810	$1,199.08	$1,199.10	$1,199.10