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	$230.93	5.398%	$243.3956	$243.40	$243.40	$243.40
Purchase #2	$43.65	3.319%	$45.0987	$45.10	$45.10	$45.10
Purchase #3	$122.96	11.345%	$136.9098	$136.91	$136.90	$136.90
Purchase #4	$227.66	12.627%	$256.4066	$256.41	$256.40	$256.40
Purchase #5	$182.88	6.874%	$195.4512	$195.45	$195.45	$195.50
Purchase #6	$173.79	13.305%	$196.9128	$196.91	$196.90	$196.90
Purchase #7	$226.94	10.225%	$250.1446	$250.14	$250.15	$250.10
7 purchase totals =	$1,208.81		$1,324.3193	$1,324.32	$1,324.30	$1,324.30