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	$97.54	9.513%	$106.819	$106.82	$106.80	$106.80
Purchase #2	$206.31	9.428%	$225.7609	$225.76	$225.75	$225.80
Purchase #3	$99.27	3.782%	$103.0244	$103.02	$103.00	$103.00
Purchase #4	$134.94	13.833%	$153.6063	$153.61	$153.60	$153.60
Purchase #5	$144.62	10.797%	$160.2346	$160.23	$160.25	$160.20
Purchase #6	$199.72	12.783%	$225.2502	$225.25	$225.25	$225.30
Purchase #7	$206.59	9.276%	$225.7533	$225.75	$225.75	$225.80
7 purchase totals =	$1,088.99		$1,200.4487	$1,200.44	$1,200.40	$1,200.50