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	$212.86	10.331%	$234.8506	$234.85	$234.85	$234.90
Purchase #2	$187.38	8.532%	$203.3673	$203.37	$203.35	$203.40
Purchase #3	$150.35	3.171%	$155.1176	$155.12	$155.10	$155.10
Purchase #4	$103.41	7.444%	$111.1078	$111.11	$111.10	$111.10
Purchase #5	$188.68	6.225%	$200.4253	$200.43	$200.45	$200.40
Purchase #6	$232.54	7.291%	$249.4945	$249.49	$249.50	$249.50
Purchase #7	$152.33	9.356%	$166.582	$166.58	$166.60	$166.60
7 purchase totals =	$1,227.55		$1,320.9451	$1,320.95	$1,320.95	$1,321.00