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	$76.48	9.529%	$83.7678	$83.77	$83.75	$83.80
Purchase #2	$172.40	13.771%	$196.1412	$196.14	$196.15	$196.10
Purchase #3	$223.58	4.561%	$233.7775	$233.78	$233.80	$233.80
Purchase #4	$99.84	5.507%	$105.3382	$105.34	$105.35	$105.30
Purchase #5	$238.30	6.759%	$254.4067	$254.41	$254.40	$254.40
Purchase #6	$165.74	6.584%	$176.6523	$176.65	$176.65	$176.70
Purchase #7	$54.32	11.223%	$60.4163	$60.42	$60.40	$60.40
7 purchase totals =	$1,030.66		$1,110.5000	$1,110.51	$1,110.50	$1,110.50