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	$150.38	10.554%	$166.2511	$166.25	$166.25	$166.30
Purchase #2	$148.43	10.869%	$164.5629	$164.56	$164.55	$164.60
Purchase #3	$46.30	5.133%	$48.6766	$48.68	$48.70	$48.70
Purchase #4	$138.37	3.761%	$143.5741	$143.57	$143.55	$143.60
Purchase #5	$34.61	3.333%	$35.7636	$35.76	$35.75	$35.80
Purchase #6	$184.73	4.774%	$193.549	$193.55	$193.55	$193.50
Purchase #7	$230.80	8.685%	$250.845	$250.85	$250.85	$250.80
7 purchase totals =	$933.62		$1,003.2223	$1,003.22	$1,003.20	$1,003.30