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	$195.89	3.726%	$203.1889	$203.19	$203.20	$203.20
Purchase #2	$209.80	4.344%	$218.9137	$218.91	$218.90	$218.90
Purchase #3	$141.79	9.242%	$154.8942	$154.89	$154.90	$154.90
Purchase #4	$29.45	13.142%	$33.3203	$33.32	$33.30	$33.30
Purchase #5	$170.52	11.225%	$189.6609	$189.66	$189.65	$189.70
Purchase #6	$138.34	13.408%	$156.8886	$156.89	$156.90	$156.90
Purchase #7	$190.37	13.772%	$216.5878	$216.59	$216.60	$216.60
7 purchase totals =	$1,076.16		$1,173.4544	$1,173.45	$1,173.45	$1,173.50