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	$120.63	9.771%	$132.4168	$132.42	$132.40	$132.40
Purchase #2	$17.38	8.669%	$18.8867	$18.89	$18.90	$18.90
Purchase #3	$201.29	4.726%	$210.803	$210.80	$210.80	$210.80
Purchase #4	$89.75	11.666%	$100.2202	$100.22	$100.20	$100.20
Purchase #5	$138.46	3.238%	$142.9433	$142.94	$142.95	$142.90
Purchase #6	$218.33	4.615%	$228.4059	$228.41	$228.40	$228.40
Purchase #7	$230.58	7.781%	$248.5214	$248.52	$248.50	$248.50
7 purchase totals =	$1,016.42		$1,082.1973	$1,082.20	$1,082.15	$1,082.10