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	$120.26	9.352%	$131.5067	$131.51	$131.50	$131.50
Purchase #2	$35.25	3.646%	$36.5352	$36.54	$36.55	$36.50
Purchase #3	$238.79	13.378%	$270.7353	$270.74	$270.75	$270.70
Purchase #4	$244.85	12.429%	$275.2824	$275.28	$275.30	$275.30
Purchase #5	$33.83	9.160%	$36.9288	$36.93	$36.95	$36.90
Purchase #6	$144.34	7.251%	$154.8061	$154.81	$154.80	$154.80
Purchase #7	$222.78	8.400%	$241.4935	$241.49	$241.50	$241.50
7 purchase totals =	$1,040.10		$1,147.2880	$1,147.30	$1,147.35	$1,147.20