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	$189.80	5.835%	$200.8748	$200.87	$200.85	$200.90
Purchase #2	$135.93	11.412%	$151.4423	$151.44	$151.45	$151.40
Purchase #3	$125.38	8.549%	$136.0987	$136.10	$136.10	$136.10
Purchase #4	$86.48	4.350%	$90.2419	$90.24	$90.25	$90.20
Purchase #5	$141.75	4.787%	$148.5356	$148.54	$148.55	$148.50
Purchase #6	$87.31	4.555%	$91.287	$91.29	$91.30	$91.30
Purchase #7	$100.89	13.668%	$114.6796	$114.68	$114.70	$114.70
7 purchase totals =	$867.54		$933.1599	$933.16	$933.20	$933.10