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	$200.72	3.712%	$208.1707	$208.17	$208.15	$208.20
Purchase #2	$139.88	7.347%	$150.157	$150.16	$150.15	$150.20
Purchase #3	$98.30	13.296%	$111.37	$111.37	$111.35	$111.40
Purchase #4	$237.71	8.874%	$258.8044	$258.80	$258.80	$258.80
Purchase #5	$75.51	8.473%	$81.908	$81.91	$81.90	$81.90
Purchase #6	$29.98	12.409%	$33.7002	$33.70	$33.70	$33.70
Purchase #7	$100.76	8.220%	$109.0425	$109.04	$109.05	$109.00
7 purchase totals =	$882.86		$953.1528	$953.15	$953.10	$953.20