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	$181.47	6.339%	$192.9734	$192.97	$192.95	$193.00
Purchase #2	$105.85	12.572%	$119.1575	$119.16	$119.15	$119.20
Purchase #3	$52.99	3.328%	$54.7535	$54.75	$54.75	$54.80
Purchase #4	$205.45	6.212%	$218.2126	$218.21	$218.20	$218.20
Purchase #5	$28.79	12.342%	$32.3433	$32.34	$32.35	$32.30
Purchase #6	$189.46	3.767%	$196.597	$196.60	$196.60	$196.60
Purchase #7	$7.39	6.745%	$7.8885	$7.89	$7.90	$7.90
7 purchase totals =	$771.40		$821.9258	$821.92	$821.90	$822.00