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	$72.59	4.527%	$75.8761	$75.88	$75.90	$75.90
Purchase #2	$194.54	9.830%	$213.6633	$213.66	$213.65	$213.70
Purchase #3	$66.29	9.720%	$72.7334	$72.73	$72.75	$72.70
Purchase #4	$176.31	11.548%	$196.6703	$196.67	$196.65	$196.70
Purchase #5	$21.36	6.742%	$22.8001	$22.80	$22.80	$22.80
Purchase #6	$117.30	11.659%	$130.976	$130.98	$131.00	$131.00
Purchase #7	$18.71	7.617%	$20.1351	$20.14	$20.15	$20.10
7 purchase totals =	$667.10		$732.8543	$732.86	$732.90	$732.90