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	$132.76	13.132%	$150.194	$150.19	$150.20	$150.20
Purchase #2	$151.81	10.150%	$167.2187	$167.22	$167.20	$167.20
Purchase #3	$114.78	10.267%	$126.5645	$126.56	$126.55	$126.60
Purchase #4	$192.69	13.398%	$218.5066	$218.51	$218.50	$218.50
Purchase #5	$176.45	5.174%	$185.5795	$185.58	$185.60	$185.60
Purchase #6	$144.96	10.865%	$160.7099	$160.71	$160.70	$160.70
Purchase #7	$58.40	10.517%	$64.5419	$64.54	$64.55	$64.50
7 purchase totals =	$971.85		$1,073.3151	$1,073.31	$1,073.30	$1,073.30