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	$79.95	8.339%	$86.617	$86.62	$86.60	$86.60
Purchase #2	$238.79	10.854%	$264.7083	$264.71	$264.70	$264.70
Purchase #3	$230.35	4.650%	$241.0613	$241.06	$241.05	$241.10
Purchase #4	$226.85	9.829%	$249.1471	$249.15	$249.15	$249.10
Purchase #5	$66.63	8.156%	$72.0643	$72.06	$72.05	$72.10
Purchase #6	$51.61	5.224%	$54.3061	$54.31	$54.30	$54.30
Purchase #7	$111.42	13.399%	$126.3492	$126.35	$126.35	$126.30
7 purchase totals =	$1,005.60		$1,094.2533	$1,094.26	$1,094.20	$1,094.20