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	$195.35	13.644%	$222.0036	$222.00	$222.00	$222.00
Purchase #2	$202.85	13.328%	$229.8858	$229.89	$229.90	$229.90
Purchase #3	$238.37	3.127%	$245.8238	$245.82	$245.80	$245.80
Purchase #4	$64.42	11.741%	$71.9836	$71.98	$72.00	$72.00
Purchase #5	$203.87	9.764%	$223.7759	$223.78	$223.80	$223.80
Purchase #6	$172.25	7.829%	$185.7355	$185.74	$185.75	$185.70
Purchase #7	$94.60	12.318%	$106.2528	$106.25	$106.25	$106.30
7 purchase totals =	$1,171.71		$1,285.4610	$1,285.46	$1,285.50	$1,285.50