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	$54.85	9.185%	$59.888	$59.89	$59.90	$59.90
Purchase #2	$37.91	13.180%	$42.9065	$42.91	$42.90	$42.90
Purchase #3	$135.33	10.750%	$149.878	$149.88	$149.90	$149.90
Purchase #4	$109.25	3.400%	$112.9645	$112.96	$112.95	$113.00
Purchase #5	$202.27	4.206%	$210.7775	$210.78	$210.80	$210.80
Purchase #6	$57.30	9.797%	$62.9137	$62.91	$62.90	$62.90
Purchase #7	$60.33	4.265%	$62.9031	$62.90	$62.90	$62.90
7 purchase totals =	$657.24		$702.2313	$702.23	$702.25	$702.30