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	$217.83	11.780%	$243.4904	$243.49	$243.50	$243.50
Purchase #2	$156.94	5.722%	$165.9201	$165.92	$165.90	$165.90
Purchase #3	$77.62	3.275%	$80.1621	$80.16	$80.15	$80.20
Purchase #4	$100.71	13.849%	$114.6573	$114.66	$114.65	$114.70
Purchase #5	$216.47	11.144%	$240.5934	$240.59	$240.60	$240.60
Purchase #6	$201.70	11.343%	$224.5788	$224.58	$224.60	$224.60
Purchase #7	$100.66	10.209%	$110.9364	$110.94	$110.95	$110.90
7 purchase totals =	$1,071.93		$1,180.3385	$1,180.34	$1,180.35	$1,180.40