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	$200.71	13.363%	$227.5309	$227.53	$227.55	$227.50
Purchase #2	$83.67	6.650%	$89.2341	$89.23	$89.25	$89.20
Purchase #3	$165.89	12.606%	$186.8021	$186.80	$186.80	$186.80
Purchase #4	$139.74	12.594%	$157.3389	$157.34	$157.35	$157.30
Purchase #5	$143.53	7.278%	$153.9761	$153.98	$154.00	$154.00
Purchase #6	$137.41	11.187%	$152.7821	$152.78	$152.80	$152.80
Purchase #7	$49.54	13.475%	$56.2155	$56.22	$56.20	$56.20
7 purchase totals =	$920.49		$1,023.8797	$1,023.88	$1,023.95	$1,023.80