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	$91.45	10.756%	$101.2864	$101.29	$101.30	$101.30
Purchase #2	$98.36	4.198%	$102.4892	$102.49	$102.50	$102.50
Purchase #3	$52.51	12.868%	$59.267	$59.27	$59.25	$59.30
Purchase #4	$87.31	4.810%	$91.5096	$91.51	$91.50	$91.50
Purchase #5	$102.37	5.219%	$107.7127	$107.71	$107.70	$107.70
Purchase #6	$241.60	3.445%	$249.9231	$249.92	$249.90	$249.90
Purchase #7	$147.69	5.259%	$155.457	$155.46	$155.45	$155.50
7 purchase totals =	$821.29		$867.6450	$867.65	$867.60	$867.70