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	$94.89	5.284%	$99.904	$99.90	$99.90	$99.90
Purchase #2	$118.69	6.466%	$126.3645	$126.36	$126.35	$126.40
Purchase #3	$191.36	9.820%	$210.1516	$210.15	$210.15	$210.20
Purchase #4	$167.33	5.721%	$176.9029	$176.90	$176.90	$176.90
Purchase #5	$147.47	9.284%	$161.1611	$161.16	$161.15	$161.20
Purchase #6	$81.93	9.319%	$89.5651	$89.57	$89.55	$89.60
Purchase #7	$140.31	7.643%	$151.0339	$151.03	$151.05	$151.00
7 purchase totals =	$941.98		$1,015.0831	$1,015.07	$1,015.05	$1,015.20