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	$246.63	4.795%	$258.4559	$258.46	$258.45	$258.50
Purchase #2	$67.82	5.817%	$71.7651	$71.77	$71.75	$71.80
Purchase #3	$66.81	8.627%	$72.5737	$72.57	$72.55	$72.60
Purchase #4	$148.49	6.432%	$158.0409	$158.04	$158.05	$158.00
Purchase #5	$138.86	6.420%	$147.7748	$147.77	$147.75	$147.80
Purchase #6	$226.28	11.527%	$252.3633	$252.36	$252.35	$252.40
Purchase #7	$53.68	4.210%	$55.9399	$55.94	$55.95	$55.90
7 purchase totals =	$948.57		$1,016.9136	$1,016.91	$1,016.85	$1,017.00