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	$9.34	13.561%	$10.6066	$10.61	$10.60	$10.60
Purchase #2	$224.63	11.368%	$250.1659	$250.17	$250.15	$250.20
Purchase #3	$53.65	13.846%	$61.0784	$61.08	$61.10	$61.10
Purchase #4	$51.66	4.654%	$54.0643	$54.06	$54.05	$54.10
Purchase #5	$12.46	7.782%	$13.4296	$13.43	$13.45	$13.40
Purchase #6	$40.90	10.448%	$45.1732	$45.17	$45.15	$45.20
Purchase #7	$112.76	11.836%	$126.1063	$126.11	$126.10	$126.10
7 purchase totals =	$505.40		$560.6243	$560.63	$560.60	$560.70