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	$113.54	6.699%	$121.146	$121.15	$121.15	$121.10
Purchase #2	$119.49	6.525%	$127.2867	$127.29	$127.30	$127.30
Purchase #3	$124.86	9.637%	$136.8928	$136.89	$136.90	$136.90
Purchase #4	$29.95	8.486%	$32.4916	$32.49	$32.50	$32.50
Purchase #5	$52.90	4.376%	$55.2149	$55.21	$55.20	$55.20
Purchase #6	$29.63	9.377%	$32.4084	$32.41	$32.40	$32.40
Purchase #7	$244.33	4.116%	$254.3866	$254.39	$254.40	$254.40
7 purchase totals =	$714.70		$759.8270	$759.83	$759.85	$759.80