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	$82.61	9.750%	$90.6645	$90.66	$90.65	$90.70
Purchase #2	$163.31	9.422%	$178.6971	$178.70	$178.70	$178.70
Purchase #3	$147.79	12.124%	$165.7081	$165.71	$165.70	$165.70
Purchase #4	$79.63	13.744%	$90.5743	$90.57	$90.55	$90.60
Purchase #5	$213.63	7.400%	$229.4386	$229.44	$229.45	$229.40
Purchase #6	$42.86	8.741%	$46.6064	$46.61	$46.60	$46.60
Purchase #7	$214.28	3.242%	$221.227	$221.23	$221.25	$221.20
7 purchase totals =	$944.11		$1,022.9160	$1,022.92	$1,022.90	$1,022.90