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	$104.78	12.695%	$118.0818	$118.08	$118.10	$118.10
Purchase #2	$67.70	12.437%	$76.1198	$76.12	$76.10	$76.10
Purchase #3	$40.88	11.384%	$45.5338	$45.53	$45.55	$45.50
Purchase #4	$116.51	6.818%	$124.4537	$124.45	$124.45	$124.50
Purchase #5	$128.71	11.550%	$143.576	$143.58	$143.60	$143.60
Purchase #6	$49.97	7.650%	$53.7927	$53.79	$53.80	$53.80
Purchase #7	$118.34	11.253%	$131.6568	$131.66	$131.65	$131.70
7 purchase totals =	$626.89		$693.2146	$693.21	$693.25	$693.30