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	$247.51	10.172%	$272.6867	$272.69	$272.70	$272.70
Purchase #2	$51.99	3.376%	$53.7452	$53.75	$53.75	$53.70
Purchase #3	$41.68	11.265%	$46.3753	$46.38	$46.40	$46.40
Purchase #4	$229.94	13.810%	$261.6947	$261.69	$261.70	$261.70
Purchase #5	$93.39	12.790%	$105.3346	$105.33	$105.35	$105.30
Purchase #6	$126.52	10.771%	$140.1475	$140.15	$140.15	$140.10
Purchase #7	$116.34	6.356%	$123.7346	$123.73	$123.75	$123.70
7 purchase totals =	$907.37		$1,003.7186	$1,003.72	$1,003.80	$1,003.60