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	$94.29	7.561%	$101.4193	$101.42	$101.40	$101.40
Purchase #2	$223.34	10.695%	$247.2262	$247.23	$247.25	$247.20
Purchase #3	$60.27	11.300%	$67.0805	$67.08	$67.10	$67.10
Purchase #4	$163.61	4.756%	$171.3913	$171.39	$171.40	$171.40
Purchase #5	$118.92	13.188%	$134.6032	$134.60	$134.60	$134.60
Purchase #6	$106.32	11.844%	$118.9125	$118.91	$118.90	$118.90
Purchase #7	$75.26	3.822%	$78.1364	$78.14	$78.15	$78.10
7 purchase totals =	$842.01		$918.7694	$918.77	$918.80	$918.70