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	$67.57	5.767%	$71.4668	$71.47	$71.45	$71.50
Purchase #2	$59.65	6.212%	$63.3555	$63.36	$63.35	$63.40
Purchase #3	$142.92	5.734%	$151.115	$151.12	$151.10	$151.10
Purchase #4	$223.84	8.451%	$242.7567	$242.76	$242.75	$242.80
Purchase #5	$235.59	7.868%	$254.1262	$254.13	$254.15	$254.10
Purchase #6	$164.42	9.428%	$179.9215	$179.92	$179.90	$179.90
Purchase #7	$65.59	9.410%	$71.762	$71.76	$71.75	$71.80
7 purchase totals =	$959.58		$1,034.5037	$1,034.52	$1,034.45	$1,034.60