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	$92.27	10.863%	$102.2933	$102.29	$102.30	$102.30
Purchase #2	$238.27	6.463%	$253.6694	$253.67	$253.65	$253.70
Purchase #3	$141.45	6.511%	$150.6598	$150.66	$150.65	$150.70
Purchase #4	$92.92	9.197%	$101.4659	$101.47	$101.45	$101.50
Purchase #5	$171.65	9.256%	$187.5379	$187.54	$187.55	$187.50
Purchase #6	$192.39	9.784%	$211.2134	$211.21	$211.20	$211.20
Purchase #7	$49.90	13.224%	$56.4988	$56.50	$56.50	$56.50
7 purchase totals =	$978.85		$1,063.3385	$1,063.34	$1,063.30	$1,063.40