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	$103.85	8.587%	$112.7676	$112.77	$112.75	$112.80
Purchase #2	$213.33	12.471%	$239.9344	$239.93	$239.95	$239.90
Purchase #3	$172.82	11.345%	$192.4264	$192.43	$192.45	$192.40
Purchase #4	$26.51	6.686%	$28.2825	$28.28	$28.30	$28.30
Purchase #5	$109.68	4.332%	$114.4313	$114.43	$114.45	$114.40
Purchase #6	$189.72	7.636%	$204.207	$204.21	$204.20	$204.20
Purchase #7	$106.41	4.805%	$111.523	$111.52	$111.50	$111.50
7 purchase totals =	$922.32		$1,003.5722	$1,003.57	$1,003.60	$1,003.50