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	$47.46	8.811%	$51.6417	$51.64	$51.65	$51.60
Purchase #2	$68.71	4.409%	$71.7394	$71.74	$71.75	$71.70
Purchase #3	$175.88	8.230%	$190.3549	$190.35	$190.35	$190.40
Purchase #4	$92.61	7.308%	$99.3779	$99.38	$99.40	$99.40
Purchase #5	$49.29	6.498%	$52.4929	$52.49	$52.50	$52.50
Purchase #6	$60.33	12.872%	$68.0957	$68.10	$68.10	$68.10
Purchase #7	$82.54	10.176%	$90.9393	$90.94	$90.95	$90.90
7 purchase totals =	$576.82		$624.6418	$624.64	$624.70	$624.60