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	$209.45	13.676%	$238.0944	$238.09	$238.10	$238.10
Purchase #2	$238.40	5.375%	$251.214	$251.21	$251.20	$251.20
Purchase #3	$92.86	12.341%	$104.3199	$104.32	$104.30	$104.30
Purchase #4	$98.79	13.429%	$112.0565	$112.06	$112.05	$112.10
Purchase #5	$40.30	4.778%	$42.2255	$42.23	$42.25	$42.20
Purchase #6	$109.91	3.823%	$114.1119	$114.11	$114.10	$114.10
Purchase #7	$133.91	13.536%	$152.0361	$152.04	$152.05	$152.00
7 purchase totals =	$923.62		$1,014.0583	$1,014.06	$1,014.05	$1,014.00