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	$48.25	10.762%	$53.4427	$53.44	$53.45	$53.40
Purchase #2	$174.89	3.793%	$181.5236	$181.52	$181.50	$181.50
Purchase #3	$184.93	11.315%	$205.8548	$205.85	$205.85	$205.90
Purchase #4	$37.56	4.151%	$39.1191	$39.12	$39.10	$39.10
Purchase #5	$90.73	12.333%	$101.9197	$101.92	$101.90	$101.90
Purchase #6	$64.84	13.674%	$73.7062	$73.71	$73.70	$73.70
Purchase #7	$215.30	12.870%	$243.0091	$243.01	$243.00	$243.00
7 purchase totals =	$816.50		$898.5752	$898.57	$898.50	$898.50