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	$240.53	9.577%	$263.5656	$263.57	$263.55	$263.60
Purchase #2	$154.73	7.737%	$166.7015	$166.70	$166.70	$166.70
Purchase #3	$153.50	7.651%	$165.2443	$165.24	$165.25	$165.20
Purchase #4	$165.73	11.571%	$184.9066	$184.91	$184.90	$184.90
Purchase #5	$247.61	4.540%	$258.8515	$258.85	$258.85	$258.90
Purchase #6	$37.54	12.254%	$42.1402	$42.14	$42.15	$42.10
Purchase #7	$86.79	4.216%	$90.4491	$90.45	$90.45	$90.40
7 purchase totals =	$1,086.43		$1,171.8588	$1,171.86	$1,171.85	$1,171.80