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	$249.99	7.338%	$268.3343	$268.33	$268.35	$268.30
Purchase #2	$50.85	7.498%	$54.6627	$54.66	$54.65	$54.70
Purchase #3	$99.45	12.862%	$112.2413	$112.24	$112.25	$112.20
Purchase #4	$115.77	7.869%	$124.8799	$124.88	$124.90	$124.90
Purchase #5	$213.62	9.800%	$234.5548	$234.55	$234.55	$234.60
Purchase #6	$205.87	5.844%	$217.901	$217.90	$217.90	$217.90
Purchase #7	$45.51	7.178%	$48.7767	$48.78	$48.80	$48.80
7 purchase totals =	$981.06		$1,061.3507	$1,061.34	$1,061.40	$1,061.40