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	$59.82	12.141%	$67.0827	$67.08	$67.10	$67.10
Purchase #2	$101.93	3.406%	$105.4017	$105.40	$105.40	$105.40
Purchase #3	$131.44	7.472%	$141.2612	$141.26	$141.25	$141.30
Purchase #4	$155.61	12.866%	$175.6308	$175.63	$175.65	$175.60
Purchase #5	$227.87	7.512%	$244.9876	$244.99	$245.00	$245.00
Purchase #6	$52.80	5.860%	$55.8941	$55.89	$55.90	$55.90
Purchase #7	$97.71	7.188%	$104.7334	$104.73	$104.75	$104.70
7 purchase totals =	$827.18		$894.9915	$894.98	$895.05	$895.00