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	$234.62	8.392%	$254.3093	$254.31	$254.30	$254.30
Purchase #2	$144.67	6.429%	$153.9708	$153.97	$153.95	$154.00
Purchase #3	$31.72	5.264%	$33.3897	$33.39	$33.40	$33.40
Purchase #4	$215.53	11.104%	$239.4625	$239.46	$239.45	$239.50
Purchase #5	$115.25	11.199%	$128.1568	$128.16	$128.15	$128.20
Purchase #6	$179.61	11.630%	$200.4986	$200.50	$200.50	$200.50
Purchase #7	$140.90	5.394%	$148.5001	$148.50	$148.50	$148.50
7 purchase totals =	$1,062.30		$1,158.2878	$1,158.29	$1,158.25	$1,158.40