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	$200.37	4.692%	$209.7714	$209.77	$209.75	$209.80
Purchase #2	$98.76	3.850%	$102.5623	$102.56	$102.55	$102.60
Purchase #3	$128.58	13.440%	$145.8612	$145.86	$145.85	$145.90
Purchase #4	$110.44	8.465%	$119.7887	$119.79	$119.80	$119.80
Purchase #5	$139.48	11.861%	$156.0237	$156.02	$156.00	$156.00
Purchase #6	$247.68	3.536%	$256.438	$256.44	$256.45	$256.40
Purchase #7	$158.73	9.661%	$174.0649	$174.06	$174.05	$174.10
7 purchase totals =	$1,084.04		$1,164.5102	$1,164.50	$1,164.45	$1,164.60