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	$58.33	7.630%	$62.7806	$62.78	$62.80	$62.80
Purchase #2	$177.31	12.643%	$199.7273	$199.73	$199.75	$199.70
Purchase #3	$225.55	8.632%	$245.0195	$245.02	$245.00	$245.00
Purchase #4	$100.48	10.833%	$111.365	$111.37	$111.35	$111.40
Purchase #5	$90.25	11.356%	$100.4988	$100.50	$100.50	$100.50
Purchase #6	$167.85	4.599%	$175.5694	$175.57	$175.55	$175.60
Purchase #7	$27.95	4.612%	$29.2391	$29.24	$29.25	$29.20
7 purchase totals =	$847.72		$924.1997	$924.21	$924.20	$924.20