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	$90.85	12.625%	$102.3198	$102.32	$102.30	$102.30
Purchase #2	$184.79	13.731%	$210.1635	$210.16	$210.15	$210.20
Purchase #3	$103.92	8.678%	$112.9382	$112.94	$112.95	$112.90
Purchase #4	$92.73	3.769%	$96.225	$96.23	$96.25	$96.20
Purchase #5	$78.49	13.532%	$89.1113	$89.11	$89.10	$89.10
Purchase #6	$197.32	6.204%	$209.5617	$209.56	$209.55	$209.60
Purchase #7	$96.74	11.686%	$108.045	$108.05	$108.05	$108.00
7 purchase totals =	$844.84		$928.3645	$928.37	$928.35	$928.30