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	$29.39	11.588%	$32.7957	$32.80	$32.80	$32.80
Purchase #2	$88.78	6.230%	$94.311	$94.31	$94.30	$94.30
Purchase #3	$214.26	3.834%	$222.4747	$222.47	$222.45	$222.50
Purchase #4	$201.89	13.600%	$229.347	$229.35	$229.35	$229.30
Purchase #5	$226.46	13.299%	$256.5769	$256.58	$256.60	$256.60
Purchase #6	$173.78	12.854%	$196.1177	$196.12	$196.10	$196.10
Purchase #7	$179.93	3.777%	$186.726	$186.73	$186.75	$186.70
7 purchase totals =	$1,114.49		$1,218.3490	$1,218.36	$1,218.35	$1,218.30