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	$191.98	3.773%	$199.2234	$199.22	$199.20	$199.20
Purchase #2	$82.53	6.750%	$88.1008	$88.10	$88.10	$88.10
Purchase #3	$62.92	7.397%	$67.5742	$67.57	$67.55	$67.60
Purchase #4	$221.32	5.520%	$233.5369	$233.54	$233.55	$233.50
Purchase #5	$141.72	11.486%	$157.998	$158.00	$158.00	$158.00
Purchase #6	$208.58	6.617%	$222.3817	$222.38	$222.40	$222.40
Purchase #7	$39.85	6.461%	$42.4247	$42.42	$42.40	$42.40
7 purchase totals =	$948.90		$1,011.2397	$1,011.23	$1,011.20	$1,011.20