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	$90.28	5.752%	$95.4729	$95.47	$95.45	$95.50
Purchase #2	$91.68	6.433%	$97.5778	$97.58	$97.60	$97.60
Purchase #3	$113.95	6.110%	$120.9123	$120.91	$120.90	$120.90
Purchase #4	$110.72	9.118%	$120.8154	$120.82	$120.80	$120.80
Purchase #5	$136.62	11.409%	$152.207	$152.21	$152.20	$152.20
Purchase #6	$175.75	11.529%	$196.0122	$196.01	$196.00	$196.00
Purchase #7	$111.55	10.319%	$123.0608	$123.06	$123.05	$123.10
7 purchase totals =	$830.55		$906.0584	$906.06	$906.00	$906.10