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	$109.88	8.379%	$119.0868	$119.09	$119.10	$119.10
Purchase #2	$213.33	7.557%	$229.4513	$229.45	$229.45	$229.50
Purchase #3	$169.85	12.633%	$191.3072	$191.31	$191.30	$191.30
Purchase #4	$221.79	4.525%	$231.826	$231.83	$231.85	$231.80
Purchase #5	$29.74	8.104%	$32.1501	$32.15	$32.15	$32.20
Purchase #6	$95.36	7.724%	$102.7256	$102.73	$102.75	$102.70
Purchase #7	$116.38	9.761%	$127.7399	$127.74	$127.75	$127.70
7 purchase totals =	$956.33		$1,034.2869	$1,034.30	$1,034.35	$1,034.30