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	$42.37	9.341%	$46.3278	$46.33	$46.35	$46.30
Purchase #2	$234.59	3.133%	$241.9397	$241.94	$241.95	$241.90
Purchase #3	$147.91	12.107%	$165.8175	$165.82	$165.80	$165.80
Purchase #4	$151.52	5.516%	$159.8778	$159.88	$159.90	$159.90
Purchase #5	$225.49	3.333%	$233.0056	$233.01	$233.00	$233.00
Purchase #6	$123.90	8.593%	$134.5467	$134.55	$134.55	$134.50
Purchase #7	$29.47	5.403%	$31.0623	$31.06	$31.05	$31.10
7 purchase totals =	$955.25		$1,012.5774	$1,012.59	$1,012.60	$1,012.50