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	$84.40	9.494%	$92.4129	$92.41	$92.40	$92.40
Purchase #2	$120.90	5.790%	$127.9001	$127.90	$127.90	$127.90
Purchase #3	$128.88	13.565%	$146.3626	$146.36	$146.35	$146.40
Purchase #4	$36.67	9.332%	$40.092	$40.09	$40.10	$40.10
Purchase #5	$170.30	12.494%	$191.5773	$191.58	$191.60	$191.60
Purchase #6	$236.58	11.163%	$262.9894	$262.99	$263.00	$263.00
Purchase #7	$68.58	3.721%	$71.1319	$71.13	$71.15	$71.10
7 purchase totals =	$846.31		$932.4662	$932.46	$932.50	$932.50