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	$146.86	11.566%	$163.8458	$163.85	$163.85	$163.80
Purchase #2	$21.54	3.874%	$22.3745	$22.37	$22.35	$22.40
Purchase #3	$236.93	11.676%	$264.5939	$264.59	$264.60	$264.60
Purchase #4	$57.78	3.540%	$59.8254	$59.83	$59.85	$59.80
Purchase #5	$222.79	9.130%	$243.1307	$243.13	$243.15	$243.10
Purchase #6	$221.82	12.396%	$249.3168	$249.32	$249.30	$249.30
Purchase #7	$223.99	8.421%	$242.8522	$242.85	$242.85	$242.90
7 purchase totals =	$1,131.71		$1,245.9393	$1,245.94	$1,245.95	$1,245.90