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	$58.69	5.451%	$61.8892	$61.89	$61.90	$61.90
Purchase #2	$37.75	12.730%	$42.5556	$42.56	$42.55	$42.60
Purchase #3	$243.95	8.825%	$265.4786	$265.48	$265.50	$265.50
Purchase #4	$55.79	3.481%	$57.732	$57.73	$57.75	$57.70
Purchase #5	$150.30	6.802%	$160.5234	$160.52	$160.50	$160.50
Purchase #6	$40.67	9.550%	$44.554	$44.55	$44.55	$44.60
Purchase #7	$36.50	5.421%	$38.4787	$38.48	$38.50	$38.50
7 purchase totals =	$623.65		$671.2115	$671.21	$671.25	$671.30