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	$29.82	12.154%	$33.4443	$33.44	$33.45	$33.40
Purchase #2	$214.34	11.748%	$239.5207	$239.52	$239.50	$239.50
Purchase #3	$136.38	13.573%	$154.8909	$154.89	$154.90	$154.90
Purchase #4	$239.35	10.691%	$264.9389	$264.94	$264.95	$264.90
Purchase #5	$167.27	3.124%	$172.4955	$172.50	$172.50	$172.50
Purchase #6	$179.98	3.464%	$186.2145	$186.21	$186.20	$186.20
Purchase #7	$221.59	9.852%	$243.421	$243.42	$243.40	$243.40
7 purchase totals =	$1,188.73		$1,294.9258	$1,294.92	$1,294.90	$1,294.80