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	$78.43	9.152%	$85.6079	$85.61	$85.60	$85.60
Purchase #2	$41.84	9.750%	$45.9194	$45.92	$45.90	$45.90
Purchase #3	$45.92	9.301%	$50.191	$50.19	$50.20	$50.20
Purchase #4	$61.98	11.136%	$68.8821	$68.88	$68.90	$68.90
Purchase #5	$21.31	12.460%	$23.9652	$23.97	$23.95	$24.00
Purchase #6	$169.43	12.870%	$191.2356	$191.24	$191.25	$191.20
Purchase #7	$54.68	4.636%	$57.215	$57.22	$57.20	$57.20
7 purchase totals =	$473.59		$523.0162	$523.03	$523.00	$523.00