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	$118.36	13.468%	$134.3007	$134.30	$134.30	$134.30
Purchase #2	$87.65	11.235%	$97.4975	$97.50	$97.50	$97.50
Purchase #3	$29.71	7.661%	$31.9861	$31.99	$32.00	$32.00
Purchase #4	$154.98	6.396%	$164.8925	$164.89	$164.90	$164.90
Purchase #5	$79.90	7.388%	$85.803	$85.80	$85.80	$85.80
Purchase #6	$196.39	9.199%	$214.4559	$214.46	$214.45	$214.50
Purchase #7	$53.98	9.782%	$59.2603	$59.26	$59.25	$59.30
7 purchase totals =	$720.97		$788.1960	$788.20	$788.20	$788.30