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	$82.79	8.255%	$89.6243	$89.62	$89.60	$89.60
Purchase #2	$214.48	12.272%	$240.801	$240.80	$240.80	$240.80
Purchase #3	$59.52	5.207%	$62.6192	$62.62	$62.60	$62.60
Purchase #4	$69.65	7.579%	$74.9288	$74.93	$74.95	$74.90
Purchase #5	$233.69	11.195%	$259.8516	$259.85	$259.85	$259.90
Purchase #6	$50.39	7.791%	$54.3159	$54.32	$54.30	$54.30
Purchase #7	$248.45	6.517%	$264.6415	$264.64	$264.65	$264.60
7 purchase totals =	$958.97		$1,046.7823	$1,046.78	$1,046.75	$1,046.70