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	$57.77	13.250%	$65.4245	$65.42	$65.40	$65.40
Purchase #2	$115.31	3.685%	$119.5592	$119.56	$119.55	$119.60
Purchase #3	$156.88	12.142%	$175.9284	$175.93	$175.95	$175.90
Purchase #4	$144.37	7.827%	$155.6698	$155.67	$155.65	$155.70
Purchase #5	$240.92	11.563%	$268.7776	$268.78	$268.80	$268.80
Purchase #6	$122.75	13.614%	$139.4612	$139.46	$139.45	$139.50
Purchase #7	$115.89	7.784%	$124.9109	$124.91	$124.90	$124.90
7 purchase totals =	$953.89		$1,049.7316	$1,049.73	$1,049.70	$1,049.80