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	$171.67	5.710%	$181.4724	$181.47	$181.45	$181.50
Purchase #2	$95.35	10.610%	$105.4666	$105.47	$105.45	$105.50
Purchase #3	$146.81	4.615%	$153.5853	$153.59	$153.60	$153.60
Purchase #4	$120.47	10.433%	$133.0386	$133.04	$133.05	$133.00
Purchase #5	$19.69	13.465%	$22.3413	$22.34	$22.35	$22.30
Purchase #6	$7.59	5.686%	$8.0216	$8.02	$8.00	$8.00
Purchase #7	$76.79	7.270%	$82.3726	$82.37	$82.35	$82.40
7 purchase totals =	$638.37		$686.2984	$686.30	$686.25	$686.30