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	$235.36	11.788%	$263.1042	$263.10	$263.10	$263.10
Purchase #2	$97.95	12.144%	$109.845	$109.85	$109.85	$109.80
Purchase #3	$114.75	11.364%	$127.7902	$127.79	$127.80	$127.80
Purchase #4	$124.37	3.332%	$128.514	$128.51	$128.50	$128.50
Purchase #5	$78.69	8.828%	$85.6368	$85.64	$85.65	$85.60
Purchase #6	$55.84	12.733%	$62.9501	$62.95	$62.95	$63.00
Purchase #7	$144.73	5.239%	$152.3124	$152.31	$152.30	$152.30
7 purchase totals =	$851.69		$930.1527	$930.15	$930.15	$930.10