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	$127.43	10.654%	$141.0064	$141.01	$141.00	$141.00
Purchase #2	$163.54	10.329%	$180.432	$180.43	$180.45	$180.40
Purchase #3	$205.29	13.160%	$232.3062	$232.31	$232.30	$232.30
Purchase #4	$179.35	9.753%	$196.842	$196.84	$196.85	$196.80
Purchase #5	$86.45	11.537%	$96.4237	$96.42	$96.40	$96.40
Purchase #6	$31.70	8.407%	$34.365	$34.37	$34.35	$34.40
Purchase #7	$55.70	7.566%	$59.9143	$59.91	$59.90	$59.90
7 purchase totals =	$849.46		$941.2896	$941.29	$941.25	$941.20