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	$33.92	4.416%	$35.4179	$35.42	$35.40	$35.40
Purchase #2	$52.50	11.796%	$58.6929	$58.69	$58.70	$58.70
Purchase #3	$156.45	5.818%	$165.5523	$165.55	$165.55	$165.60
Purchase #4	$36.33	3.425%	$37.5743	$37.57	$37.55	$37.60
Purchase #5	$155.52	11.555%	$173.4903	$173.49	$173.50	$173.50
Purchase #6	$170.63	8.483%	$185.1045	$185.10	$185.10	$185.10
Purchase #7	$69.55	3.116%	$71.7172	$71.72	$71.70	$71.70
7 purchase totals =	$674.90		$727.5494	$727.54	$727.50	$727.60