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	$70.65	10.117%	$77.7977	$77.80	$77.80	$77.80
Purchase #2	$122.40	13.864%	$139.3695	$139.37	$139.35	$139.40
Purchase #3	$142.63	7.533%	$153.3743	$153.37	$153.35	$153.40
Purchase #4	$185.67	13.814%	$211.3185	$211.32	$211.30	$211.30
Purchase #5	$65.71	10.480%	$72.5964	$72.60	$72.60	$72.60
Purchase #6	$222.67	6.283%	$236.6604	$236.66	$236.65	$236.70
Purchase #7	$134.55	5.457%	$141.8924	$141.89	$141.90	$141.90
7 purchase totals =	$944.28		$1,033.0092	$1,033.01	$1,032.95	$1,033.10