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	$196.51	11.397%	$218.9062	$218.91	$218.90	$218.90
Purchase #2	$82.28	8.569%	$89.3306	$89.33	$89.35	$89.30
Purchase #3	$204.98	12.199%	$229.9855	$229.99	$230.00	$230.00
Purchase #4	$100.32	11.269%	$111.6251	$111.63	$111.65	$111.60
Purchase #5	$84.64	7.486%	$90.9762	$90.98	$91.00	$91.00
Purchase #6	$45.35	10.185%	$49.9689	$49.97	$49.95	$50.00
Purchase #7	$206.93	5.759%	$218.8471	$218.85	$218.85	$218.80
7 purchase totals =	$921.01		$1,009.6396	$1,009.66	$1,009.70	$1,009.60