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	$91.92	10.466%	$101.5403	$101.54	$101.55	$101.50
Purchase #2	$142.42	7.199%	$152.6728	$152.67	$152.65	$152.70
Purchase #3	$28.73	11.406%	$32.0069	$32.01	$32.00	$32.00
Purchase #4	$36.35	12.464%	$40.8807	$40.88	$40.90	$40.90
Purchase #5	$12.53	8.834%	$13.6369	$13.64	$13.65	$13.60
Purchase #6	$68.93	10.651%	$76.2717	$76.27	$76.25	$76.30
Purchase #7	$241.36	6.224%	$256.3822	$256.38	$256.40	$256.40
7 purchase totals =	$622.24		$673.3915	$673.39	$673.40	$673.40