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	$108.51	10.743%	$120.1672	$120.17	$120.15	$120.20
Purchase #2	$26.78	6.292%	$28.465	$28.47	$28.45	$28.50
Purchase #3	$49.43	6.127%	$52.4586	$52.46	$52.45	$52.50
Purchase #4	$165.96	4.446%	$173.3386	$173.34	$173.35	$173.30
Purchase #5	$153.79	13.491%	$174.5378	$174.54	$174.55	$174.50
Purchase #6	$163.54	4.637%	$171.1233	$171.12	$171.10	$171.10
Purchase #7	$131.74	11.233%	$146.5384	$146.54	$146.55	$146.50
7 purchase totals =	$799.75		$866.6289	$866.64	$866.60	$866.60