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	$80.45	9.438%	$88.0429	$88.04	$88.05	$88.00
Purchase #2	$195.71	9.587%	$214.4727	$214.47	$214.45	$214.50
Purchase #3	$174.48	8.700%	$189.6598	$189.66	$189.65	$189.70
Purchase #4	$74.90	7.868%	$80.7931	$80.79	$80.80	$80.80
Purchase #5	$218.72	8.442%	$237.1843	$237.18	$237.20	$237.20
Purchase #6	$180.36	9.123%	$196.8142	$196.81	$196.80	$196.80
Purchase #7	$94.89	4.613%	$99.2673	$99.27	$99.25	$99.30
7 purchase totals =	$1,019.51		$1,106.2343	$1,106.22	$1,106.20	$1,106.30