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	$240.33	3.143%	$247.8836	$247.88	$247.90	$247.90
Purchase #2	$165.29	11.171%	$183.7545	$183.75	$183.75	$183.80
Purchase #3	$69.53	4.155%	$72.419	$72.42	$72.40	$72.40
Purchase #4	$149.28	6.511%	$158.9996	$159.00	$159.00	$159.00
Purchase #5	$141.96	7.434%	$152.5133	$152.51	$152.50	$152.50
Purchase #6	$80.92	5.346%	$85.246	$85.25	$85.25	$85.20
Purchase #7	$106.82	10.201%	$117.7167	$117.72	$117.70	$117.70
7 purchase totals =	$954.13		$1,018.5327	$1,018.53	$1,018.50	$1,018.50