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	$88.36	3.843%	$91.7557	$91.76	$91.75	$91.80
Purchase #2	$246.59	3.368%	$254.8952	$254.90	$254.90	$254.90
Purchase #3	$133.30	4.831%	$139.7397	$139.74	$139.75	$139.70
Purchase #4	$237.49	4.166%	$247.3838	$247.38	$247.40	$247.40
Purchase #5	$59.51	10.558%	$65.7931	$65.79	$65.80	$65.80
Purchase #6	$52.77	12.755%	$59.5008	$59.50	$59.50	$59.50
Purchase #7	$11.26	12.507%	$12.6683	$12.67	$12.65	$12.70
7 purchase totals =	$829.28		$871.7366	$871.74	$871.75	$871.80