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	$190.94	4.443%	$199.4235	$199.42	$199.40	$199.40
Purchase #2	$54.38	10.216%	$59.9355	$59.94	$59.95	$59.90
Purchase #3	$230.52	6.596%	$245.7251	$245.73	$245.75	$245.70
Purchase #4	$189.85	5.797%	$200.8556	$200.86	$200.85	$200.90
Purchase #5	$239.74	3.391%	$247.8696	$247.87	$247.85	$247.90
Purchase #6	$32.83	12.750%	$37.0158	$37.02	$37.00	$37.00
Purchase #7	$120.37	5.474%	$126.9591	$126.96	$126.95	$127.00
7 purchase totals =	$1,058.63		$1,117.7842	$1,117.80	$1,117.75	$1,117.80