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	$195.72	5.330%	$206.1519	$206.15	$206.15	$206.20
Purchase #2	$187.89	6.445%	$199.9995	$200.00	$200.00	$200.00
Purchase #3	$55.35	11.823%	$61.894	$61.89	$61.90	$61.90
Purchase #4	$127.72	10.159%	$140.6951	$140.70	$140.70	$140.70
Purchase #5	$210.44	5.343%	$221.6838	$221.68	$221.70	$221.70
Purchase #6	$123.72	13.253%	$140.1166	$140.12	$140.10	$140.10
Purchase #7	$24.71	11.769%	$27.6181	$27.62	$27.60	$27.60
7 purchase totals =	$925.55		$998.1590	$998.16	$998.15	$998.20