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	$192.68	7.551%	$207.2293	$207.23	$207.25	$207.20
Purchase #2	$231.54	7.864%	$249.7483	$249.75	$249.75	$249.70
Purchase #3	$99.28	11.865%	$111.0596	$111.06	$111.05	$111.10
Purchase #4	$191.82	4.330%	$200.1258	$200.13	$200.15	$200.10
Purchase #5	$125.55	4.777%	$131.5475	$131.55	$131.55	$131.50
Purchase #6	$19.64	6.609%	$20.938	$20.94	$20.95	$20.90
Purchase #7	$155.25	13.503%	$176.2134	$176.21	$176.20	$176.20
7 purchase totals =	$1,015.76		$1,096.8619	$1,096.87	$1,096.90	$1,096.70