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	$224.55	6.329%	$238.7618	$238.76	$238.75	$238.80
Purchase #2	$209.67	6.104%	$222.4683	$222.47	$222.45	$222.50
Purchase #3	$147.82	7.302%	$158.6138	$158.61	$158.60	$158.60
Purchase #4	$110.34	5.357%	$116.2509	$116.25	$116.25	$116.30
Purchase #5	$50.33	7.130%	$53.9185	$53.92	$53.90	$53.90
Purchase #6	$102.52	3.283%	$105.8857	$105.89	$105.90	$105.90
Purchase #7	$191.38	9.267%	$209.1152	$209.12	$209.10	$209.10
7 purchase totals =	$1,036.61		$1,105.0142	$1,105.02	$1,104.95	$1,105.10