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	$59.32	11.450%	$66.1121	$66.11	$66.10	$66.10
Purchase #2	$86.82	6.869%	$92.7837	$92.78	$92.80	$92.80
Purchase #3	$137.76	11.657%	$153.8187	$153.82	$153.80	$153.80
Purchase #4	$152.45	6.837%	$162.873	$162.87	$162.85	$162.90
Purchase #5	$204.56	9.289%	$223.5616	$223.56	$223.55	$223.60
Purchase #6	$243.53	9.552%	$266.792	$266.79	$266.80	$266.80
Purchase #7	$37.54	8.851%	$40.8627	$40.86	$40.85	$40.90
7 purchase totals =	$921.98		$1,006.8038	$1,006.79	$1,006.75	$1,006.90