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	$175.26	6.119%	$185.9842	$185.98	$186.00	$186.00
Purchase #2	$149.32	8.655%	$162.2436	$162.24	$162.25	$162.20
Purchase #3	$222.98	8.510%	$241.9556	$241.96	$241.95	$242.00
Purchase #4	$150.82	11.704%	$168.472	$168.47	$168.45	$168.50
Purchase #5	$102.50	7.590%	$110.2798	$110.28	$110.30	$110.30
Purchase #6	$122.42	13.659%	$139.1413	$139.14	$139.15	$139.10
Purchase #7	$190.62	9.333%	$208.4106	$208.41	$208.40	$208.40
7 purchase totals =	$1,113.92		$1,216.4871	$1,216.48	$1,216.50	$1,216.50