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	$214.85	13.431%	$243.7065	$243.71	$243.70	$243.70
Purchase #2	$94.94	7.804%	$102.3491	$102.35	$102.35	$102.30
Purchase #3	$90.37	7.143%	$96.8251	$96.83	$96.85	$96.80
Purchase #4	$40.37	13.644%	$45.8781	$45.88	$45.90	$45.90
Purchase #5	$159.77	3.796%	$165.8349	$165.83	$165.85	$165.80
Purchase #6	$179.77	11.421%	$200.3015	$200.30	$200.30	$200.30
Purchase #7	$19.28	11.132%	$21.4262	$21.43	$21.45	$21.40
7 purchase totals =	$799.35		$876.3214	$876.33	$876.40	$876.20