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	$205.64	9.414%	$224.9989	$225.00	$225.00	$225.00
Purchase #2	$51.79	11.141%	$57.5599	$57.56	$57.55	$57.60
Purchase #3	$107.64	4.340%	$112.3116	$112.31	$112.30	$112.30
Purchase #4	$141.73	7.163%	$151.8821	$151.88	$151.90	$151.90
Purchase #5	$92.69	8.431%	$100.5047	$100.50	$100.50	$100.50
Purchase #6	$91.73	13.767%	$104.3585	$104.36	$104.35	$104.40
Purchase #7	$131.83	5.561%	$139.1611	$139.16	$139.15	$139.20
7 purchase totals =	$823.05		$890.7768	$890.77	$890.75	$890.90