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	$33.74	8.415%	$36.5792	$36.58	$36.60	$36.60
Purchase #2	$142.71	9.486%	$156.2475	$156.25	$156.25	$156.20
Purchase #3	$85.50	6.102%	$90.7172	$90.72	$90.70	$90.70
Purchase #4	$11.89	5.578%	$12.5532	$12.55	$12.55	$12.60
Purchase #5	$179.80	3.575%	$186.2279	$186.23	$186.25	$186.20
Purchase #6	$167.98	3.559%	$173.9584	$173.96	$173.95	$174.00
Purchase #7	$215.39	13.669%	$244.8317	$244.83	$244.85	$244.80
7 purchase totals =	$837.01		$901.1151	$901.12	$901.15	$901.10