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	$133.62	8.807%	$145.3879	$145.39	$145.40	$145.40
Purchase #2	$190.87	10.214%	$210.3655	$210.37	$210.35	$210.40
Purchase #3	$176.42	7.251%	$189.2122	$189.21	$189.20	$189.20
Purchase #4	$213.89	12.554%	$240.7418	$240.74	$240.75	$240.70
Purchase #5	$127.62	11.783%	$142.6575	$142.66	$142.65	$142.70
Purchase #6	$39.60	7.192%	$42.448	$42.45	$42.45	$42.40
Purchase #7	$28.69	9.251%	$31.3441	$31.34	$31.35	$31.30
7 purchase totals =	$910.71		$1,002.1570	$1,002.16	$1,002.15	$1,002.10