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	$37.48	3.471%	$38.7809	$38.78	$38.80	$38.80
Purchase #2	$45.36	4.726%	$47.5037	$47.50	$47.50	$47.50
Purchase #3	$149.61	13.515%	$169.8298	$169.83	$169.85	$169.80
Purchase #4	$215.82	4.395%	$225.3053	$225.31	$225.30	$225.30
Purchase #5	$18.40	13.856%	$20.9495	$20.95	$20.95	$20.90
Purchase #6	$111.64	5.257%	$117.5089	$117.51	$117.50	$117.50
Purchase #7	$215.67	8.767%	$234.5778	$234.58	$234.60	$234.60
7 purchase totals =	$793.98		$854.4559	$854.46	$854.50	$854.40