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	$114.92	7.450%	$123.4815	$123.48	$123.50	$123.50
Purchase #2	$122.67	10.595%	$135.6669	$135.67	$135.65	$135.70
Purchase #3	$10.82	6.136%	$11.4839	$11.48	$11.50	$11.50
Purchase #4	$194.71	5.185%	$204.8057	$204.81	$204.80	$204.80
Purchase #5	$67.27	8.390%	$72.914	$72.91	$72.90	$72.90
Purchase #6	$78.27	4.121%	$81.4955	$81.50	$81.50	$81.50
Purchase #7	$78.48	7.672%	$84.501	$84.50	$84.50	$84.50
7 purchase totals =	$667.14		$714.3485	$714.35	$714.35	$714.40