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	$174.85	4.464%	$182.6553	$182.66	$182.65	$182.70
Purchase #2	$100.69	10.813%	$111.5776	$111.58	$111.60	$111.60
Purchase #3	$79.97	11.628%	$89.2689	$89.27	$89.25	$89.30
Purchase #4	$17.29	13.751%	$19.6675	$19.67	$19.65	$19.70
Purchase #5	$90.48	9.203%	$98.8069	$98.81	$98.80	$98.80
Purchase #6	$48.25	5.494%	$50.9009	$50.90	$50.90	$50.90
Purchase #7	$47.83	7.404%	$51.3713	$51.37	$51.35	$51.40
7 purchase totals =	$559.36		$604.2484	$604.26	$604.20	$604.40