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	$32.32	10.170%	$35.6069	$35.61	$35.60	$35.60
Purchase #2	$139.29	9.375%	$152.3484	$152.35	$152.35	$152.30
Purchase #3	$228.73	6.422%	$243.419	$243.42	$243.40	$243.40
Purchase #4	$13.79	13.121%	$15.5994	$15.60	$15.60	$15.60
Purchase #5	$38.92	7.355%	$41.7826	$41.78	$41.80	$41.80
Purchase #6	$157.61	9.591%	$172.7264	$172.73	$172.75	$172.70
Purchase #7	$246.78	13.485%	$280.0583	$280.06	$280.05	$280.10
7 purchase totals =	$857.44		$941.5410	$941.55	$941.55	$941.50