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	$33.86	10.421%	$37.3886	$37.39	$37.40	$37.40
Purchase #2	$106.29	7.856%	$114.6401	$114.64	$114.65	$114.60
Purchase #3	$60.82	11.406%	$67.7571	$67.76	$67.75	$67.80
Purchase #4	$39.32	8.696%	$42.7393	$42.74	$42.75	$42.70
Purchase #5	$238.64	11.809%	$266.821	$266.82	$266.80	$266.80
Purchase #6	$226.28	11.533%	$252.3769	$252.38	$252.40	$252.40
Purchase #7	$94.31	8.684%	$102.4999	$102.50	$102.50	$102.50
7 purchase totals =	$799.52		$884.2229	$884.23	$884.25	$884.20