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	$192.98	13.615%	$219.2542	$219.25	$219.25	$219.30
Purchase #2	$90.72	9.641%	$99.4663	$99.47	$99.45	$99.50
Purchase #3	$96.26	11.696%	$107.5186	$107.52	$107.50	$107.50
Purchase #4	$71.43	9.445%	$78.1766	$78.18	$78.20	$78.20
Purchase #5	$247.73	11.258%	$275.6194	$275.62	$275.60	$275.60
Purchase #6	$250.71	10.702%	$277.541	$277.54	$277.55	$277.50
Purchase #7	$66.80	12.737%	$75.3083	$75.31	$75.30	$75.30
7 purchase totals =	$1,016.63		$1,132.8844	$1,132.89	$1,132.85	$1,132.90