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	$143.59	6.712%	$153.2278	$153.23	$153.25	$153.20
Purchase #2	$159.95	13.297%	$181.2186	$181.22	$181.20	$181.20
Purchase #3	$59.41	5.856%	$62.889	$62.89	$62.90	$62.90
Purchase #4	$173.50	5.772%	$183.5144	$183.51	$183.50	$183.50
Purchase #5	$71.59	5.272%	$75.3642	$75.36	$75.35	$75.40
Purchase #6	$37.84	13.538%	$42.9628	$42.96	$42.95	$43.00
Purchase #7	$143.68	4.585%	$150.2677	$150.27	$150.25	$150.30
7 purchase totals =	$789.56		$849.4445	$849.44	$849.40	$849.50