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	$244.38	9.370%	$267.2784	$267.28	$267.30	$267.30
Purchase #2	$227.58	7.769%	$245.2607	$245.26	$245.25	$245.30
Purchase #3	$63.83	13.611%	$72.5179	$72.52	$72.50	$72.50
Purchase #4	$205.88	3.705%	$213.5079	$213.51	$213.50	$213.50
Purchase #5	$249.35	9.603%	$273.2951	$273.30	$273.30	$273.30
Purchase #6	$78.90	5.133%	$82.9499	$82.95	$82.95	$82.90
Purchase #7	$203.67	6.499%	$216.9065	$216.91	$216.90	$216.90
7 purchase totals =	$1,273.59		$1,371.7164	$1,371.73	$1,371.70	$1,371.70