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	$184.56	13.760%	$209.9555	$209.96	$209.95	$210.00
Purchase #2	$59.45	11.277%	$66.1542	$66.15	$66.15	$66.20
Purchase #3	$20.88	7.319%	$22.4082	$22.41	$22.40	$22.40
Purchase #4	$248.30	4.730%	$260.0446	$260.04	$260.05	$260.00
Purchase #5	$176.77	7.750%	$190.4697	$190.47	$190.45	$190.50
Purchase #6	$119.82	9.783%	$131.542	$131.54	$131.55	$131.50
Purchase #7	$190.32	11.241%	$211.7139	$211.71	$211.70	$211.70
7 purchase totals =	$1,000.10		$1,092.2881	$1,092.28	$1,092.25	$1,092.30