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	$71.63	3.765%	$74.3269	$74.33	$74.35	$74.30
Purchase #2	$188.68	4.211%	$196.6253	$196.63	$196.65	$196.60
Purchase #3	$58.41	5.293%	$61.5016	$61.50	$61.50	$61.50
Purchase #4	$108.83	13.810%	$123.8594	$123.86	$123.85	$123.90
Purchase #5	$127.48	4.670%	$133.4333	$133.43	$133.45	$133.40
Purchase #6	$166.93	3.460%	$172.7058	$172.71	$172.70	$172.70
Purchase #7	$210.28	4.765%	$220.2998	$220.30	$220.30	$220.30
7 purchase totals =	$932.24		$982.7521	$982.76	$982.80	$982.70