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	$225.67	7.728%	$243.1098	$243.11	$243.10	$243.10
Purchase #2	$52.81	12.817%	$59.5787	$59.58	$59.60	$59.60
Purchase #3	$79.37	3.115%	$81.8424	$81.84	$81.85	$81.80
Purchase #4	$21.68	11.829%	$24.2445	$24.24	$24.25	$24.20
Purchase #5	$118.63	10.833%	$131.4812	$131.48	$131.50	$131.50
Purchase #6	$232.50	5.128%	$244.4226	$244.42	$244.40	$244.40
Purchase #7	$127.42	10.696%	$141.0488	$141.05	$141.05	$141.00
7 purchase totals =	$858.08		$925.7280	$925.72	$925.75	$925.60