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	$119.49	5.546%	$126.1169	$126.12	$126.10	$126.10
Purchase #2	$111.52	13.494%	$126.5685	$126.57	$126.55	$126.60
Purchase #3	$96.90	3.123%	$99.9262	$99.93	$99.95	$99.90
Purchase #4	$191.84	8.836%	$208.791	$208.79	$208.80	$208.80
Purchase #5	$34.71	12.843%	$39.1678	$39.17	$39.15	$39.20
Purchase #6	$20.69	10.508%	$22.8641	$22.86	$22.85	$22.90
Purchase #7	$103.73	5.378%	$109.3086	$109.31	$109.30	$109.30
7 purchase totals =	$678.88		$732.7431	$732.75	$732.70	$732.80