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	$125.33	6.829%	$133.8888	$133.89	$133.90	$133.90
Purchase #2	$15.36	3.842%	$15.9501	$15.95	$15.95	$16.00
Purchase #3	$139.67	11.610%	$155.8857	$155.89	$155.90	$155.90
Purchase #4	$127.31	3.299%	$131.51	$131.51	$131.50	$131.50
Purchase #5	$133.36	12.771%	$150.3914	$150.39	$150.40	$150.40
Purchase #6	$202.38	3.713%	$209.8944	$209.89	$209.90	$209.90
Purchase #7	$106.56	3.256%	$110.0296	$110.03	$110.05	$110.00
7 purchase totals =	$849.97		$907.5500	$907.55	$907.60	$907.60