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	$196.86	9.239%	$215.0479	$215.05	$215.05	$215.00
Purchase #2	$223.54	3.749%	$231.9205	$231.92	$231.90	$231.90
Purchase #3	$172.41	11.142%	$191.6199	$191.62	$191.60	$191.60
Purchase #4	$85.86	3.507%	$88.8711	$88.87	$88.85	$88.90
Purchase #5	$218.98	10.674%	$242.3539	$242.35	$242.35	$242.40
Purchase #6	$165.42	8.365%	$179.2574	$179.26	$179.25	$179.30
Purchase #7	$166.58	4.378%	$173.8729	$173.87	$173.85	$173.90
7 purchase totals =	$1,229.65		$1,322.9436	$1,322.94	$1,322.85	$1,323.00