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	$143.34	6.668%	$152.8979	$152.90	$152.90	$152.90
Purchase #2	$58.82	4.532%	$61.4857	$61.49	$61.50	$61.50
Purchase #3	$31.43	11.482%	$35.0388	$35.04	$35.05	$35.00
Purchase #4	$127.94	13.686%	$145.4499	$145.45	$145.45	$145.40
Purchase #5	$63.46	13.380%	$71.9509	$71.95	$71.95	$72.00
Purchase #6	$233.75	8.795%	$254.3083	$254.31	$254.30	$254.30
Purchase #7	$180.61	10.799%	$200.1141	$200.11	$200.10	$200.10
7 purchase totals =	$839.35		$921.2456	$921.25	$921.25	$921.20