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	$217.71	12.466%	$244.8497	$244.85	$244.85	$244.80
Purchase #2	$170.61	12.284%	$191.5677	$191.57	$191.55	$191.60
Purchase #3	$137.42	12.836%	$155.0592	$155.06	$155.05	$155.10
Purchase #4	$147.48	4.735%	$154.4632	$154.46	$154.45	$154.50
Purchase #5	$66.95	6.732%	$71.4571	$71.46	$71.45	$71.50
Purchase #6	$224.89	10.846%	$249.2816	$249.28	$249.30	$249.30
Purchase #7	$23.32	4.604%	$24.3937	$24.39	$24.40	$24.40
7 purchase totals =	$988.38		$1,091.0722	$1,091.07	$1,091.05	$1,091.20