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	$242.32	5.501%	$255.65	$255.65	$255.65	$255.70
Purchase #2	$64.88	4.607%	$67.869	$67.87	$67.85	$67.90
Purchase #3	$61.73	5.645%	$65.2147	$65.21	$65.20	$65.20
Purchase #4	$94.96	4.117%	$98.8695	$98.87	$98.85	$98.90
Purchase #5	$230.80	6.480%	$245.7558	$245.76	$245.75	$245.80
Purchase #6	$127.53	13.339%	$144.5412	$144.54	$144.55	$144.50
Purchase #7	$55.41	5.521%	$58.4692	$58.47	$58.45	$58.50
7 purchase totals =	$877.63		$936.3694	$936.37	$936.30	$936.50