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	$65.69	10.841%	$72.8115	$72.81	$72.80	$72.80
Purchase #2	$103.57	10.340%	$114.2791	$114.28	$114.30	$114.30
Purchase #3	$197.46	13.749%	$224.6088	$224.61	$224.60	$224.60
Purchase #4	$100.88	8.483%	$109.4377	$109.44	$109.45	$109.40
Purchase #5	$132.31	9.817%	$145.2989	$145.30	$145.30	$145.30
Purchase #6	$240.59	4.569%	$251.5826	$251.58	$251.60	$251.60
Purchase #7	$120.96	5.236%	$127.2935	$127.29	$127.30	$127.30
7 purchase totals =	$961.46		$1,045.3121	$1,045.31	$1,045.35	$1,045.30