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	$130.88	13.798%	$148.9388	$148.94	$148.95	$148.90
Purchase #2	$61.71	8.800%	$67.1405	$67.14	$67.15	$67.10
Purchase #3	$74.77	4.658%	$78.2528	$78.25	$78.25	$78.30
Purchase #4	$60.33	12.237%	$67.7126	$67.71	$67.70	$67.70
Purchase #5	$227.99	12.230%	$255.8732	$255.87	$255.85	$255.90
Purchase #6	$105.64	11.432%	$117.7168	$117.72	$117.70	$117.70
Purchase #7	$172.31	5.414%	$181.6389	$181.64	$181.65	$181.60
7 purchase totals =	$833.63		$917.2736	$917.27	$917.25	$917.20