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	$200.76	10.250%	$221.3379	$221.34	$221.35	$221.30
Purchase #2	$188.61	10.496%	$208.4065	$208.41	$208.40	$208.40
Purchase #3	$25.38	9.816%	$27.8713	$27.87	$27.85	$27.90
Purchase #4	$240.70	9.190%	$262.8203	$262.82	$262.80	$262.80
Purchase #5	$89.89	13.469%	$101.9973	$102.00	$102.00	$102.00
Purchase #6	$239.28	6.795%	$255.5391	$255.54	$255.55	$255.50
Purchase #7	$127.42	7.350%	$136.7854	$136.79	$136.80	$136.80
7 purchase totals =	$1,112.04		$1,214.7578	$1,214.77	$1,214.75	$1,214.70