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	$195.63	11.329%	$217.7929	$217.79	$217.80	$217.80
Purchase #2	$61.33	9.624%	$67.2324	$67.23	$67.25	$67.20
Purchase #3	$38.64	12.380%	$43.4236	$43.42	$43.40	$43.40
Purchase #4	$131.95	10.610%	$145.9499	$145.95	$145.95	$145.90
Purchase #5	$85.30	8.687%	$92.71	$92.71	$92.70	$92.70
Purchase #6	$59.59	3.543%	$61.7013	$61.70	$61.70	$61.70
Purchase #7	$61.37	9.398%	$67.1376	$67.14	$67.15	$67.10
7 purchase totals =	$633.81		$695.9477	$695.94	$695.95	$695.80