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	$75.54	8.514%	$81.9715	$81.97	$81.95	$82.00
Purchase #2	$125.43	4.782%	$131.4281	$131.43	$131.45	$131.40
Purchase #3	$100.77	4.651%	$105.4568	$105.46	$105.45	$105.50
Purchase #4	$134.49	7.194%	$144.1652	$144.17	$144.15	$144.20
Purchase #5	$49.99	8.837%	$54.4076	$54.41	$54.40	$54.40
Purchase #6	$36.84	12.615%	$41.4874	$41.49	$41.50	$41.50
Purchase #7	$241.98	4.623%	$253.1667	$253.17	$253.15	$253.20
7 purchase totals =	$765.04		$812.0833	$812.10	$812.05	$812.20