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	$57.56	7.138%	$61.6686	$61.67	$61.65	$61.70
Purchase #2	$189.81	11.494%	$211.6268	$211.63	$211.65	$211.60
Purchase #3	$98.48	13.638%	$111.9107	$111.91	$111.90	$111.90
Purchase #4	$206.52	5.816%	$218.5312	$218.53	$218.55	$218.50
Purchase #5	$221.82	5.331%	$233.6452	$233.65	$233.65	$233.60
Purchase #6	$137.25	6.742%	$146.5034	$146.50	$146.50	$146.50
Purchase #7	$176.80	13.395%	$200.4824	$200.48	$200.50	$200.50
7 purchase totals =	$1,088.24		$1,184.3683	$1,184.37	$1,184.40	$1,184.30