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	$65.37	3.288%	$67.5194	$67.52	$67.50	$67.50
Purchase #2	$54.46	4.440%	$56.878	$56.88	$56.90	$56.90
Purchase #3	$233.72	7.342%	$250.8797	$250.88	$250.90	$250.90
Purchase #4	$26.34	9.380%	$28.8107	$28.81	$28.80	$28.80
Purchase #5	$157.54	11.117%	$175.0537	$175.05	$175.05	$175.10
Purchase #6	$20.37	11.145%	$22.6402	$22.64	$22.65	$22.60
Purchase #7	$132.74	13.583%	$150.7701	$150.77	$150.75	$150.80
7 purchase totals =	$690.54		$752.5518	$752.55	$752.55	$752.60