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	$41.31	11.673%	$46.1321	$46.13	$46.15	$46.10
Purchase #2	$77.95	4.574%	$81.5154	$81.52	$81.50	$81.50
Purchase #3	$21.71	3.596%	$22.4907	$22.49	$22.50	$22.50
Purchase #4	$29.67	7.393%	$31.8635	$31.86	$31.85	$31.90
Purchase #5	$152.50	12.616%	$171.7394	$171.74	$171.75	$171.70
Purchase #6	$73.39	12.504%	$82.5667	$82.57	$82.55	$82.60
Purchase #7	$17.58	9.262%	$19.2083	$19.21	$19.20	$19.20
7 purchase totals =	$414.11		$455.5161	$455.52	$455.50	$455.50