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	$116.56	5.637%	$123.1305	$123.13	$123.15	$123.10
Purchase #2	$95.33	8.265%	$103.209	$103.21	$103.20	$103.20
Purchase #3	$109.54	6.749%	$116.9329	$116.93	$116.95	$116.90
Purchase #4	$249.57	3.440%	$258.1552	$258.16	$258.15	$258.20
Purchase #5	$136.32	5.572%	$143.9158	$143.92	$143.90	$143.90
Purchase #6	$147.38	13.675%	$167.5342	$167.53	$167.55	$167.50
Purchase #7	$125.33	3.661%	$129.9183	$129.92	$129.90	$129.90
7 purchase totals =	$980.03		$1,042.7959	$1,042.80	$1,042.80	$1,042.70