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	$89.46	7.774%	$96.4146	$96.41	$96.40	$96.40
Purchase #2	$191.43	6.660%	$204.1792	$204.18	$204.20	$204.20
Purchase #3	$87.67	3.140%	$90.4228	$90.42	$90.40	$90.40
Purchase #4	$166.82	13.325%	$189.0488	$189.05	$189.05	$189.00
Purchase #5	$193.38	12.338%	$217.2392	$217.24	$217.25	$217.20
Purchase #6	$85.63	4.437%	$89.4294	$89.43	$89.45	$89.40
Purchase #7	$20.97	8.335%	$22.7178	$22.72	$22.70	$22.70
7 purchase totals =	$835.36		$909.4518	$909.45	$909.45	$909.30