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	$93.33	5.260%	$98.2392	$98.24	$98.25	$98.20
Purchase #2	$41.89	13.110%	$47.3818	$47.38	$47.40	$47.40
Purchase #3	$95.76	4.318%	$99.8949	$99.89	$99.90	$99.90
Purchase #4	$233.88	11.325%	$260.3669	$260.37	$260.35	$260.40
Purchase #5	$242.90	10.725%	$268.951	$268.95	$268.95	$269.00
Purchase #6	$49.56	9.870%	$54.4516	$54.45	$54.45	$54.50
Purchase #7	$191.96	11.739%	$214.4942	$214.49	$214.50	$214.50
7 purchase totals =	$949.28		$1,043.7796	$1,043.77	$1,043.80	$1,043.90