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	$155.85	6.432%	$165.8743	$165.87	$165.85	$165.90
Purchase #2	$88.35	13.862%	$100.5971	$100.60	$100.60	$100.60
Purchase #3	$151.82	12.782%	$171.2256	$171.23	$171.25	$171.20
Purchase #4	$239.44	13.232%	$271.1227	$271.12	$271.10	$271.10
Purchase #5	$186.88	3.816%	$194.0113	$194.01	$194.00	$194.00
Purchase #6	$153.34	9.682%	$168.1864	$168.19	$168.20	$168.20
Purchase #7	$32.26	3.686%	$33.4491	$33.45	$33.45	$33.40
7 purchase totals =	$1,007.94		$1,104.4665	$1,104.47	$1,104.45	$1,104.40