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	$130.78	10.619%	$144.6675	$144.67	$144.65	$144.70
Purchase #2	$97.29	3.443%	$100.6397	$100.64	$100.65	$100.60
Purchase #3	$54.49	12.605%	$61.3585	$61.36	$61.35	$61.40
Purchase #4	$246.91	12.285%	$277.2429	$277.24	$277.25	$277.20
Purchase #5	$228.96	11.655%	$255.6453	$255.65	$255.65	$255.60
Purchase #6	$236.72	12.256%	$265.7324	$265.73	$265.75	$265.70
Purchase #7	$45.79	13.417%	$51.9336	$51.93	$51.95	$51.90
7 purchase totals =	$1,040.94		$1,157.2199	$1,157.22	$1,157.25	$1,157.10