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	$191.68	6.483%	$204.1066	$204.11	$204.10	$204.10
Purchase #2	$205.33	13.713%	$233.4869	$233.49	$233.50	$233.50
Purchase #3	$235.95	11.268%	$262.5368	$262.54	$262.55	$262.50
Purchase #4	$241.46	13.538%	$274.1489	$274.15	$274.15	$274.10
Purchase #5	$151.84	8.280%	$164.4124	$164.41	$164.40	$164.40
Purchase #6	$162.55	5.748%	$171.8934	$171.89	$171.90	$171.90
Purchase #7	$170.94	7.362%	$183.5246	$183.52	$183.50	$183.50
7 purchase totals =	$1,359.75		$1,494.1096	$1,494.11	$1,494.10	$1,494.00