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	$191.42	13.723%	$217.6886	$217.69	$217.70	$217.70
Purchase #2	$39.49	3.493%	$40.8694	$40.87	$40.85	$40.90
Purchase #3	$19.31	10.595%	$21.3559	$21.36	$21.35	$21.40
Purchase #4	$64.36	10.740%	$71.2723	$71.27	$71.25	$71.30
Purchase #5	$94.28	6.161%	$100.0886	$100.09	$100.10	$100.10
Purchase #6	$167.80	6.141%	$178.1046	$178.10	$178.10	$178.10
Purchase #7	$250.41	6.702%	$267.1925	$267.19	$267.20	$267.20
7 purchase totals =	$827.07		$896.5719	$896.57	$896.55	$896.70