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	$173.38	10.870%	$192.2264	$192.23	$192.25	$192.20
Purchase #2	$172.75	3.632%	$179.0243	$179.02	$179.00	$179.00
Purchase #3	$167.76	10.349%	$185.1215	$185.12	$185.10	$185.10
Purchase #4	$12.59	9.335%	$13.7653	$13.77	$13.75	$13.80
Purchase #5	$199.59	9.456%	$218.4632	$218.46	$218.45	$218.50
Purchase #6	$180.71	10.180%	$199.1063	$199.11	$199.10	$199.10
Purchase #7	$17.98	13.762%	$20.4544	$20.45	$20.45	$20.50
7 purchase totals =	$924.76		$1,008.1614	$1,008.16	$1,008.10	$1,008.20