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	$45.62	8.202%	$49.3618	$49.36	$49.35	$49.40
Purchase #2	$78.28	9.254%	$85.524	$85.52	$85.50	$85.50
Purchase #3	$168.26	3.670%	$174.4351	$174.44	$174.45	$174.40
Purchase #4	$119.65	9.666%	$131.2154	$131.22	$131.20	$131.20
Purchase #5	$18.35	13.603%	$20.8462	$20.85	$20.85	$20.80
Purchase #6	$151.63	13.767%	$172.5049	$172.50	$172.50	$172.50
Purchase #7	$64.97	5.336%	$68.4368	$68.44	$68.45	$68.40
7 purchase totals =	$646.76		$702.3242	$702.33	$702.30	$702.20