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	$55.27	12.718%	$62.2992	$62.30	$62.30	$62.30
Purchase #2	$230.97	12.612%	$260.0999	$260.10	$260.10	$260.10
Purchase #3	$189.81	13.582%	$215.59	$215.59	$215.60	$215.60
Purchase #4	$223.76	10.705%	$247.7135	$247.71	$247.70	$247.70
Purchase #5	$165.58	3.215%	$170.9034	$170.90	$170.90	$170.90
Purchase #6	$59.29	5.592%	$62.6055	$62.61	$62.60	$62.60
Purchase #7	$228.26	3.433%	$236.0962	$236.10	$236.10	$236.10
7 purchase totals =	$1,152.94		$1,255.3077	$1,255.31	$1,255.30	$1,255.30