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	$205.58	6.736%	$219.4279	$219.43	$219.45	$219.40
Purchase #2	$126.90	4.226%	$132.2628	$132.26	$132.25	$132.30
Purchase #3	$229.63	6.784%	$245.2081	$245.21	$245.20	$245.20
Purchase #4	$64.92	11.606%	$72.4546	$72.45	$72.45	$72.50
Purchase #5	$186.59	4.171%	$194.3727	$194.37	$194.35	$194.40
Purchase #6	$224.91	8.256%	$243.4786	$243.48	$243.50	$243.50
Purchase #7	$62.28	6.840%	$66.54	$66.54	$66.55	$66.50
7 purchase totals =	$1,100.81		$1,173.7447	$1,173.74	$1,173.75	$1,173.80