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	$35.68	7.535%	$38.3685	$38.37	$38.35	$38.40
Purchase #2	$170.89	11.183%	$190.0006	$190.00	$190.00	$190.00
Purchase #3	$211.34	10.256%	$233.015	$233.02	$233.00	$233.00
Purchase #4	$182.50	4.617%	$190.926	$190.93	$190.95	$190.90
Purchase #5	$150.57	5.264%	$158.496	$158.50	$158.50	$158.50
Purchase #6	$83.67	12.261%	$93.9288	$93.93	$93.95	$93.90
Purchase #7	$173.70	3.413%	$179.6284	$179.63	$179.65	$179.60
7 purchase totals =	$1,008.35		$1,084.3633	$1,084.38	$1,084.40	$1,084.30