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	$141.41	4.788%	$148.1807	$148.18	$148.20	$148.20
Purchase #2	$177.84	10.699%	$196.8671	$196.87	$196.85	$196.90
Purchase #3	$44.71	4.637%	$46.7832	$46.78	$46.80	$46.80
Purchase #4	$59.61	3.197%	$61.5157	$61.52	$61.50	$61.50
Purchase #5	$109.91	13.305%	$124.5335	$124.53	$124.55	$124.50
Purchase #6	$23.59	7.487%	$25.3562	$25.36	$25.35	$25.40
Purchase #7	$150.42	11.859%	$168.2583	$168.26	$168.25	$168.30
7 purchase totals =	$707.49		$771.4947	$771.50	$771.50	$771.60