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	$237.30	11.483%	$264.5492	$264.55	$264.55	$264.50
Purchase #2	$177.83	11.270%	$197.8714	$197.87	$197.85	$197.90
Purchase #3	$151.64	3.168%	$156.444	$156.44	$156.45	$156.40
Purchase #4	$103.93	5.581%	$109.7303	$109.73	$109.75	$109.70
Purchase #5	$78.31	13.597%	$88.9578	$88.96	$88.95	$89.00
Purchase #6	$235.95	4.499%	$246.5654	$246.57	$246.55	$246.60
Purchase #7	$40.85	4.642%	$42.7463	$42.75	$42.75	$42.70
7 purchase totals =	$1,025.81		$1,106.8644	$1,106.87	$1,106.85	$1,106.80