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	$247.86	4.690%	$259.4846	$259.48	$259.50	$259.50
Purchase #2	$151.76	5.728%	$160.4528	$160.45	$160.45	$160.50
Purchase #3	$208.99	9.842%	$229.5588	$229.56	$229.55	$229.60
Purchase #4	$35.34	3.488%	$36.5727	$36.57	$36.55	$36.60
Purchase #5	$137.40	7.804%	$148.1227	$148.12	$148.10	$148.10
Purchase #6	$215.99	3.463%	$223.4697	$223.47	$223.45	$223.50
Purchase #7	$12.55	5.756%	$13.2724	$13.27	$13.25	$13.30
7 purchase totals =	$1,009.89		$1,070.9337	$1,070.92	$1,070.85	$1,071.10