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	$60.73	6.345%	$64.5833	$64.58	$64.60	$64.60
Purchase #2	$113.39	9.482%	$124.1416	$124.14	$124.15	$124.10
Purchase #3	$223.86	4.488%	$233.9068	$233.91	$233.90	$233.90
Purchase #4	$189.49	13.513%	$215.0958	$215.10	$215.10	$215.10
Purchase #5	$62.60	3.255%	$64.6376	$64.64	$64.65	$64.60
Purchase #6	$184.59	13.504%	$209.517	$209.52	$209.50	$209.50
Purchase #7	$204.59	12.219%	$229.5889	$229.59	$229.60	$229.60
7 purchase totals =	$1,039.25		$1,141.4710	$1,141.48	$1,141.50	$1,141.40