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	$158.94	11.318%	$176.9288	$176.93	$176.95	$176.90
Purchase #2	$174.67	12.471%	$196.4531	$196.45	$196.45	$196.50
Purchase #3	$10.38	8.165%	$11.2275	$11.23	$11.25	$11.20
Purchase #4	$104.77	6.300%	$111.3705	$111.37	$111.35	$111.40
Purchase #5	$158.90	7.327%	$170.5426	$170.54	$170.55	$170.50
Purchase #6	$58.47	11.141%	$64.9841	$64.98	$65.00	$65.00
Purchase #7	$43.54	3.800%	$45.1945	$45.19	$45.20	$45.20
7 purchase totals =	$709.67		$776.7011	$776.69	$776.75	$776.70