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	$160.53	4.652%	$167.9979	$168.00	$168.00	$168.00
Purchase #2	$26.69	5.459%	$28.147	$28.15	$28.15	$28.10
Purchase #3	$47.51	12.339%	$53.3723	$53.37	$53.35	$53.40
Purchase #4	$53.59	11.774%	$59.8997	$59.90	$59.90	$59.90
Purchase #5	$159.56	3.162%	$164.6053	$164.61	$164.60	$164.60
Purchase #6	$172.55	7.862%	$186.1159	$186.12	$186.10	$186.10
Purchase #7	$225.25	6.578%	$240.0669	$240.07	$240.05	$240.10
7 purchase totals =	$845.68		$900.2050	$900.22	$900.15	$900.20