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	$176.56	11.543%	$196.9403	$196.94	$196.95	$196.90
Purchase #2	$104.38	9.431%	$114.2241	$114.22	$114.20	$114.20
Purchase #3	$231.96	3.659%	$240.4474	$240.45	$240.45	$240.40
Purchase #4	$204.66	10.302%	$225.7441	$225.74	$225.75	$225.70
Purchase #5	$56.42	4.579%	$59.0035	$59.00	$59.00	$59.00
Purchase #6	$5.58	10.123%	$6.1449	$6.14	$6.15	$6.10
Purchase #7	$77.42	9.871%	$85.0621	$85.06	$85.05	$85.10
7 purchase totals =	$856.98		$927.5664	$927.55	$927.55	$927.40