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	$190.61	8.316%	$206.4611	$206.46	$206.45	$206.50
Purchase #2	$244.52	13.139%	$276.6475	$276.65	$276.65	$276.60
Purchase #3	$203.61	12.118%	$228.2835	$228.28	$228.30	$228.30
Purchase #4	$53.60	10.734%	$59.3534	$59.35	$59.35	$59.40
Purchase #5	$212.86	4.623%	$222.7005	$222.70	$222.70	$222.70
Purchase #6	$190.68	3.267%	$196.9095	$196.91	$196.90	$196.90
Purchase #7	$91.82	3.403%	$94.9446	$94.94	$94.95	$94.90
7 purchase totals =	$1,187.70		$1,285.3001	$1,285.29	$1,285.30	$1,285.30