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	$72.37	8.698%	$78.6647	$78.66	$78.65	$78.70
Purchase #2	$100.78	8.713%	$109.561	$109.56	$109.55	$109.60
Purchase #3	$31.34	5.769%	$33.148	$33.15	$33.15	$33.10
Purchase #4	$163.86	4.465%	$171.1763	$171.18	$171.20	$171.20
Purchase #5	$90.90	5.544%	$95.9395	$95.94	$95.95	$95.90
Purchase #6	$199.68	3.291%	$206.2515	$206.25	$206.25	$206.30
Purchase #7	$148.88	8.129%	$160.9825	$160.98	$161.00	$161.00
7 purchase totals =	$807.81		$855.7235	$855.72	$855.75	$855.80