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	$228.58	7.124%	$244.864	$244.86	$244.85	$244.90
Purchase #2	$76.28	7.647%	$82.1131	$82.11	$82.10	$82.10
Purchase #3	$154.92	4.325%	$161.6203	$161.62	$161.60	$161.60
Purchase #4	$60.44	12.135%	$67.7744	$67.77	$67.75	$67.80
Purchase #5	$180.25	9.131%	$196.7086	$196.71	$196.70	$196.70
Purchase #6	$250.56	5.335%	$263.9274	$263.93	$263.95	$263.90
Purchase #7	$38.61	13.243%	$43.7231	$43.72	$43.70	$43.70
7 purchase totals =	$989.64		$1,060.7309	$1,060.72	$1,060.65	$1,060.70