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	$203.77	9.599%	$223.3299	$223.33	$223.35	$223.30
Purchase #2	$200.30	8.448%	$217.2213	$217.22	$217.20	$217.20
Purchase #3	$209.40	11.145%	$232.7376	$232.74	$232.75	$232.70
Purchase #4	$43.67	9.386%	$47.7689	$47.77	$47.75	$47.80
Purchase #5	$157.74	6.557%	$168.083	$168.08	$168.10	$168.10
Purchase #6	$105.85	3.548%	$109.6056	$109.61	$109.60	$109.60
Purchase #7	$165.97	4.143%	$172.8461	$172.85	$172.85	$172.80
7 purchase totals =	$1,086.70		$1,171.5924	$1,171.60	$1,171.60	$1,171.50