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	$164.46	8.668%	$178.7154	$178.72	$178.70	$178.70
Purchase #2	$76.35	7.760%	$82.2748	$82.27	$82.25	$82.30
Purchase #3	$227.72	9.720%	$249.8544	$249.85	$249.85	$249.90
Purchase #4	$135.62	9.551%	$148.5731	$148.57	$148.55	$148.60
Purchase #5	$184.73	10.243%	$203.6519	$203.65	$203.65	$203.70
Purchase #6	$124.34	11.106%	$138.1492	$138.15	$138.15	$138.10
Purchase #7	$180.82	7.795%	$194.9149	$194.91	$194.90	$194.90
7 purchase totals =	$1,094.04		$1,196.1337	$1,196.12	$1,196.05	$1,196.20