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	$53.83	4.428%	$56.2136	$56.21	$56.20	$56.20
Purchase #2	$19.35	7.825%	$20.8641	$20.86	$20.85	$20.90
Purchase #3	$181.94	10.205%	$200.507	$200.51	$200.50	$200.50
Purchase #4	$12.84	6.440%	$13.6669	$13.67	$13.65	$13.70
Purchase #5	$124.49	5.469%	$131.2984	$131.30	$131.30	$131.30
Purchase #6	$227.91	7.258%	$244.4517	$244.45	$244.45	$244.50
Purchase #7	$50.29	9.264%	$54.9489	$54.95	$54.95	$54.90
7 purchase totals =	$670.65		$721.9506	$721.95	$721.90	$722.00