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	$54.26	9.388%	$59.3539	$59.35	$59.35	$59.40
Purchase #2	$218.32	8.269%	$236.3729	$236.37	$236.35	$236.40
Purchase #3	$59.57	8.405%	$64.5769	$64.58	$64.60	$64.60
Purchase #4	$43.32	6.741%	$46.2402	$46.24	$46.25	$46.20
Purchase #5	$228.75	11.185%	$254.3357	$254.34	$254.35	$254.30
Purchase #6	$231.55	3.327%	$239.2537	$239.25	$239.25	$239.30
Purchase #7	$29.75	12.334%	$33.4194	$33.42	$33.40	$33.40
7 purchase totals =	$865.52		$933.5527	$933.55	$933.55	$933.60