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	$191.57	4.830%	$200.8228	$200.82	$200.80	$200.80
Purchase #2	$51.92	10.108%	$57.1681	$57.17	$57.15	$57.20
Purchase #3	$122.91	10.514%	$135.8328	$135.83	$135.85	$135.80
Purchase #4	$119.42	7.841%	$128.7837	$128.78	$128.80	$128.80
Purchase #5	$205.89	5.153%	$216.4995	$216.50	$216.50	$216.50
Purchase #6	$24.75	4.250%	$25.8019	$25.80	$25.80	$25.80
Purchase #7	$98.73	12.560%	$111.1305	$111.13	$111.15	$111.10
7 purchase totals =	$815.19		$876.0393	$876.03	$876.05	$876.00