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	$181.36	8.266%	$196.3512	$196.35	$196.35	$196.40
Purchase #2	$101.54	10.238%	$111.9357	$111.94	$111.95	$111.90
Purchase #3	$192.66	8.306%	$208.6623	$208.66	$208.65	$208.70
Purchase #4	$242.42	13.483%	$275.1055	$275.11	$275.10	$275.10
Purchase #5	$91.30	10.406%	$100.8007	$100.80	$100.80	$100.80
Purchase #6	$192.74	10.487%	$212.9526	$212.95	$212.95	$213.00
Purchase #7	$76.50	7.109%	$81.9384	$81.94	$81.95	$81.90
7 purchase totals =	$1,078.52		$1,187.7464	$1,187.75	$1,187.75	$1,187.80