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	$76.39	9.450%	$83.6089	$83.61	$83.60	$83.60
Purchase #2	$58.25	10.140%	$64.1566	$64.16	$64.15	$64.20
Purchase #3	$72.75	10.811%	$80.615	$80.62	$80.60	$80.60
Purchase #4	$64.45	5.128%	$67.755	$67.76	$67.75	$67.80
Purchase #5	$84.66	5.201%	$89.0632	$89.06	$89.05	$89.10
Purchase #6	$27.40	13.387%	$31.068	$31.07	$31.05	$31.10
Purchase #7	$98.33	8.221%	$106.4137	$106.41	$106.40	$106.40
7 purchase totals =	$482.23		$522.6804	$522.69	$522.60	$522.80