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	$69.89	5.157%	$73.4942	$73.49	$73.50	$73.50
Purchase #2	$142.52	7.247%	$152.8484	$152.85	$152.85	$152.80
Purchase #3	$169.98	9.505%	$186.1366	$186.14	$186.15	$186.10
Purchase #4	$221.95	3.316%	$229.3099	$229.31	$229.30	$229.30
Purchase #5	$136.81	3.586%	$141.716	$141.72	$141.70	$141.70
Purchase #6	$155.47	3.472%	$160.8679	$160.87	$160.85	$160.90
Purchase #7	$110.99	11.121%	$123.3332	$123.33	$123.35	$123.30
7 purchase totals =	$1,007.61		$1,067.7062	$1,067.71	$1,067.70	$1,067.60