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	$196.27	13.334%	$222.4406	$222.44	$222.45	$222.40
Purchase #2	$235.44	3.538%	$243.7699	$243.77	$243.75	$243.80
Purchase #3	$161.40	5.699%	$170.5982	$170.60	$170.60	$170.60
Purchase #4	$171.30	8.472%	$185.8125	$185.81	$185.80	$185.80
Purchase #5	$52.52	6.380%	$55.8708	$55.87	$55.85	$55.90
Purchase #6	$67.70	5.481%	$71.4106	$71.41	$71.40	$71.40
Purchase #7	$173.90	13.421%	$197.2391	$197.24	$197.25	$197.20
7 purchase totals =	$1,058.53		$1,147.1417	$1,147.14	$1,147.10	$1,147.10