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	$154.59	9.205%	$168.82	$168.82	$168.80	$168.80
Purchase #2	$233.83	10.732%	$258.9246	$258.92	$258.90	$258.90
Purchase #3	$183.33	3.444%	$189.6439	$189.64	$189.65	$189.60
Purchase #4	$190.34	12.225%	$213.6091	$213.61	$213.60	$213.60
Purchase #5	$25.38	4.126%	$26.4272	$26.43	$26.45	$26.40
Purchase #6	$50.35	5.566%	$53.1525	$53.15	$53.15	$53.20
Purchase #7	$143.99	4.199%	$150.0361	$150.04	$150.05	$150.00
7 purchase totals =	$981.81		$1,060.6134	$1,060.61	$1,060.60	$1,060.50