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	$69.32	12.239%	$77.8041	$77.80	$77.80	$77.80
Purchase #2	$78.27	5.852%	$82.8504	$82.85	$82.85	$82.90
Purchase #3	$78.52	6.718%	$83.795	$83.80	$83.80	$83.80
Purchase #4	$91.68	6.221%	$97.3834	$97.38	$97.40	$97.40
Purchase #5	$18.98	10.375%	$20.9492	$20.95	$20.95	$20.90
Purchase #6	$190.80	10.459%	$210.7558	$210.76	$210.75	$210.80
Purchase #7	$81.31	5.771%	$86.0024	$86.00	$86.00	$86.00
7 purchase totals =	$608.88		$659.5403	$659.54	$659.55	$659.60