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	$12.77	12.662%	$14.3869	$14.39	$14.40	$14.40
Purchase #2	$223.35	10.315%	$246.3886	$246.39	$246.40	$246.40
Purchase #3	$36.83	6.625%	$39.27	$39.27	$39.25	$39.30
Purchase #4	$131.42	7.112%	$140.7666	$140.77	$140.75	$140.80
Purchase #5	$116.82	9.747%	$128.2064	$128.21	$128.20	$128.20
Purchase #6	$62.52	13.149%	$70.7408	$70.74	$70.75	$70.70
Purchase #7	$83.98	7.280%	$90.0937	$90.09	$90.10	$90.10
7 purchase totals =	$667.69		$729.8530	$729.86	$729.85	$729.90