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	$203.41	11.315%	$226.4258	$226.43	$226.45	$226.40
Purchase #2	$108.61	4.169%	$113.138	$113.14	$113.15	$113.10
Purchase #3	$94.79	9.448%	$103.7458	$103.75	$103.75	$103.70
Purchase #4	$102.57	3.142%	$105.7927	$105.79	$105.80	$105.80
Purchase #5	$244.44	8.261%	$264.6332	$264.63	$264.65	$264.60
Purchase #6	$162.89	5.682%	$172.1454	$172.15	$172.15	$172.10
Purchase #7	$229.32	6.216%	$243.5745	$243.57	$243.55	$243.60
7 purchase totals =	$1,146.03		$1,229.4554	$1,229.46	$1,229.50	$1,229.30