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	$179.98	5.598%	$190.0553	$190.06	$190.05	$190.10
Purchase #2	$21.95	5.184%	$23.0879	$23.09	$23.10	$23.10
Purchase #3	$55.30	7.274%	$59.3225	$59.32	$59.30	$59.30
Purchase #4	$19.34	7.627%	$20.8151	$20.82	$20.80	$20.80
Purchase #5	$120.69	11.213%	$134.223	$134.22	$134.20	$134.20
Purchase #6	$111.45	10.362%	$122.9984	$123.00	$123.00	$123.00
Purchase #7	$24.38	4.674%	$25.5195	$25.52	$25.50	$25.50
7 purchase totals =	$533.09		$576.0217	$576.03	$575.95	$576.00