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	$202.34	6.139%	$214.7617	$214.76	$214.75	$214.80
Purchase #2	$204.69	10.858%	$226.9152	$226.92	$226.90	$226.90
Purchase #3	$247.72	4.524%	$258.9269	$258.93	$258.95	$258.90
Purchase #4	$130.35	5.112%	$137.0135	$137.01	$137.00	$137.00
Purchase #5	$185.26	6.187%	$196.722	$196.72	$196.70	$196.70
Purchase #6	$172.49	7.521%	$185.463	$185.46	$185.45	$185.50
Purchase #7	$70.91	4.484%	$74.0896	$74.09	$74.10	$74.10
7 purchase totals =	$1,213.76		$1,293.8919	$1,293.89	$1,293.85	$1,293.90