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	$175.64	7.561%	$188.9201	$188.92	$188.90	$188.90
Purchase #2	$140.43	5.439%	$148.068	$148.07	$148.05	$148.10
Purchase #3	$201.36	6.461%	$214.3699	$214.37	$214.35	$214.40
Purchase #4	$17.88	11.739%	$19.9789	$19.98	$20.00	$20.00
Purchase #5	$159.70	5.523%	$168.5202	$168.52	$168.50	$168.50
Purchase #6	$118.40	4.205%	$123.3787	$123.38	$123.40	$123.40
Purchase #7	$6.92	3.595%	$7.1688	$7.17	$7.15	$7.20
7 purchase totals =	$820.33		$870.4046	$870.41	$870.35	$870.50