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	$58.45	3.523%	$60.5092	$60.51	$60.50	$60.50
Purchase #2	$142.29	5.761%	$150.4873	$150.49	$150.50	$150.50
Purchase #3	$108.71	5.721%	$114.9293	$114.93	$114.95	$114.90
Purchase #4	$160.54	11.685%	$179.2991	$179.30	$179.30	$179.30
Purchase #5	$137.71	11.474%	$153.5108	$153.51	$153.50	$153.50
Purchase #6	$169.94	11.348%	$189.2248	$189.22	$189.20	$189.20
Purchase #7	$141.93	11.218%	$157.8517	$157.85	$157.85	$157.90
7 purchase totals =	$919.57		$1,005.8122	$1,005.81	$1,005.80	$1,005.80