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	$247.60	4.409%	$258.5167	$258.52	$258.50	$258.50
Purchase #2	$127.57	4.733%	$133.6079	$133.61	$133.60	$133.60
Purchase #3	$183.96	3.771%	$190.8971	$190.90	$190.90	$190.90
Purchase #4	$56.37	3.451%	$58.3153	$58.32	$58.30	$58.30
Purchase #5	$113.31	12.871%	$127.8941	$127.89	$127.90	$127.90
Purchase #6	$228.86	12.387%	$257.2089	$257.21	$257.20	$257.20
Purchase #7	$59.75	13.450%	$67.7864	$67.79	$67.80	$67.80
7 purchase totals =	$1,017.42		$1,094.2264	$1,094.24	$1,094.20	$1,094.20