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	$14.59	4.205%	$15.2035	$15.20	$15.20	$15.20
Purchase #2	$233.68	13.361%	$264.902	$264.90	$264.90	$264.90
Purchase #3	$165.55	11.840%	$185.1511	$185.15	$185.15	$185.20
Purchase #4	$123.78	3.254%	$127.8078	$127.81	$127.80	$127.80
Purchase #5	$18.44	11.873%	$20.6294	$20.63	$20.65	$20.60
Purchase #6	$241.56	3.511%	$250.0412	$250.04	$250.05	$250.00
Purchase #7	$177.96	13.565%	$202.1003	$202.10	$202.10	$202.10
7 purchase totals =	$975.56		$1,065.8353	$1,065.83	$1,065.85	$1,065.80