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	$247.65	10.353%	$273.2892	$273.29	$273.30	$273.30
Purchase #2	$215.26	8.829%	$234.2653	$234.27	$234.25	$234.30
Purchase #3	$55.67	7.462%	$59.8241	$59.82	$59.80	$59.80
Purchase #4	$81.46	4.711%	$85.2976	$85.30	$85.30	$85.30
Purchase #5	$198.38	10.309%	$218.831	$218.83	$218.85	$218.80
Purchase #6	$55.48	5.746%	$58.6679	$58.67	$58.65	$58.70
Purchase #7	$180.55	4.256%	$188.2342	$188.23	$188.25	$188.20
7 purchase totals =	$1,034.45		$1,118.4093	$1,118.41	$1,118.40	$1,118.40