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	$219.29	11.203%	$243.8571	$243.86	$243.85	$243.90
Purchase #2	$137.46	8.138%	$148.6465	$148.65	$148.65	$148.60
Purchase #3	$149.45	10.335%	$164.8957	$164.90	$164.90	$164.90
Purchase #4	$185.34	13.576%	$210.5018	$210.50	$210.50	$210.50
Purchase #5	$114.40	12.828%	$129.0752	$129.08	$129.10	$129.10
Purchase #6	$34.75	13.294%	$39.3697	$39.37	$39.35	$39.40
Purchase #7	$210.77	5.776%	$222.9441	$222.94	$222.95	$222.90
7 purchase totals =	$1,051.46		$1,159.2901	$1,159.30	$1,159.30	$1,159.30