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	$204.73	3.546%	$211.9897	$211.99	$212.00	$212.00
Purchase #2	$87.73	13.693%	$99.7429	$99.74	$99.75	$99.70
Purchase #3	$65.33	7.341%	$70.1259	$70.13	$70.15	$70.10
Purchase #4	$240.78	6.150%	$255.588	$255.59	$255.60	$255.60
Purchase #5	$231.51	4.533%	$242.0043	$242.00	$242.00	$242.00
Purchase #6	$37.53	13.750%	$42.6904	$42.69	$42.70	$42.70
Purchase #7	$181.72	5.607%	$191.909	$191.91	$191.90	$191.90
7 purchase totals =	$1,049.33		$1,114.0502	$1,114.05	$1,114.10	$1,114.00