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	$18.28	3.673%	$18.9514	$18.95	$18.95	$19.00
Purchase #2	$152.86	7.638%	$164.5354	$164.54	$164.55	$164.50
Purchase #3	$150.94	3.410%	$156.0871	$156.09	$156.10	$156.10
Purchase #4	$79.87	7.409%	$85.7876	$85.79	$85.80	$85.80
Purchase #5	$208.31	9.485%	$228.0682	$228.07	$228.05	$228.10
Purchase #6	$40.34	4.450%	$42.1351	$42.14	$42.15	$42.10
Purchase #7	$51.68	13.773%	$58.7979	$58.80	$58.80	$58.80
7 purchase totals =	$702.28		$754.3627	$754.38	$754.40	$754.40