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	$81.97	3.738%	$85.034	$85.03	$85.05	$85.00
Purchase #2	$173.34	4.143%	$180.5215	$180.52	$180.50	$180.50
Purchase #3	$39.90	4.319%	$41.6233	$41.62	$41.60	$41.60
Purchase #4	$168.54	12.408%	$189.4524	$189.45	$189.45	$189.50
Purchase #5	$236.89	11.120%	$263.2322	$263.23	$263.25	$263.20
Purchase #6	$18.79	13.671%	$21.3588	$21.36	$21.35	$21.40
Purchase #7	$78.49	3.748%	$81.4318	$81.43	$81.45	$81.40
7 purchase totals =	$797.92		$862.6540	$862.64	$862.65	$862.60