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	$31.83	5.297%	$33.516	$33.52	$33.50	$33.50
Purchase #2	$78.64	4.441%	$82.1324	$82.13	$82.15	$82.10
Purchase #3	$247.81	3.150%	$255.616	$255.62	$255.60	$255.60
Purchase #4	$183.29	8.729%	$199.2894	$199.29	$199.30	$199.30
Purchase #5	$64.43	11.788%	$72.025	$72.03	$72.05	$72.00
Purchase #6	$79.41	8.270%	$85.9772	$85.98	$86.00	$86.00
Purchase #7	$151.51	9.210%	$165.4641	$165.46	$165.45	$165.50
7 purchase totals =	$836.92		$894.0201	$894.03	$894.05	$894.00