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	$151.78	13.366%	$172.0669	$172.07	$172.05	$172.10
Purchase #2	$214.38	6.424%	$228.1518	$228.15	$228.15	$228.20
Purchase #3	$212.89	7.224%	$228.2692	$228.27	$228.25	$228.30
Purchase #4	$187.90	5.656%	$198.5276	$198.53	$198.55	$198.50
Purchase #5	$41.49	8.827%	$45.1523	$45.15	$45.15	$45.20
Purchase #6	$153.55	8.544%	$166.6693	$166.67	$166.65	$166.70
Purchase #7	$89.55	4.199%	$93.3102	$93.31	$93.30	$93.30
7 purchase totals =	$1,051.54		$1,132.1473	$1,132.15	$1,132.10	$1,132.30