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	$200.63	13.339%	$227.392	$227.39	$227.40	$227.40
Purchase #2	$119.38	10.309%	$131.6869	$131.69	$131.70	$131.70
Purchase #3	$55.27	8.296%	$59.8552	$59.86	$59.85	$59.90
Purchase #4	$217.70	11.764%	$243.3102	$243.31	$243.30	$243.30
Purchase #5	$14.92	13.320%	$16.9073	$16.91	$16.90	$16.90
Purchase #6	$32.52	10.671%	$35.9902	$35.99	$36.00	$36.00
Purchase #7	$96.92	3.553%	$100.3636	$100.36	$100.35	$100.40
7 purchase totals =	$737.34		$815.5054	$815.51	$815.50	$815.60