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	$191.70	11.510%	$213.7647	$213.76	$213.75	$213.80
Purchase #2	$133.77	8.193%	$144.7298	$144.73	$144.75	$144.70
Purchase #3	$248.82	10.205%	$274.2121	$274.21	$274.20	$274.20
Purchase #4	$154.88	11.565%	$172.7919	$172.79	$172.80	$172.80
Purchase #5	$103.33	11.205%	$114.9081	$114.91	$114.90	$114.90
Purchase #6	$194.90	9.213%	$212.8561	$212.86	$212.85	$212.90
Purchase #7	$182.55	3.293%	$188.5614	$188.56	$188.55	$188.60
7 purchase totals =	$1,209.95		$1,321.8241	$1,321.82	$1,321.80	$1,321.90