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	$93.88	7.117%	$100.5614	$100.56	$100.55	$100.60
Purchase #2	$212.32	4.868%	$222.6557	$222.66	$222.65	$222.70
Purchase #3	$211.92	4.510%	$221.4776	$221.48	$221.50	$221.50
Purchase #4	$151.48	12.167%	$169.9106	$169.91	$169.90	$169.90
Purchase #5	$56.43	7.221%	$60.5048	$60.50	$60.50	$60.50
Purchase #6	$133.29	12.452%	$149.8873	$149.89	$149.90	$149.90
Purchase #7	$103.58	6.144%	$109.944	$109.94	$109.95	$109.90
7 purchase totals =	$962.90		$1,034.9414	$1,034.94	$1,034.95	$1,035.00