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	$169.34	4.771%	$177.4192	$177.42	$177.40	$177.40
Purchase #2	$227.92	10.140%	$251.0311	$251.03	$251.05	$251.00
Purchase #3	$205.28	6.611%	$218.8511	$218.85	$218.85	$218.90
Purchase #4	$147.34	4.410%	$153.8377	$153.84	$153.85	$153.80
Purchase #5	$157.55	10.362%	$173.8753	$173.88	$173.90	$173.90
Purchase #6	$64.43	11.487%	$71.8311	$71.83	$71.85	$71.80
Purchase #7	$93.76	7.241%	$100.5492	$100.55	$100.55	$100.50
7 purchase totals =	$1,065.62		$1,147.3947	$1,147.40	$1,147.45	$1,147.30