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	$132.99	8.779%	$144.6652	$144.67	$144.65	$144.70
Purchase #2	$78.33	6.558%	$83.4669	$83.47	$83.45	$83.50
Purchase #3	$243.59	13.134%	$275.5831	$275.58	$275.60	$275.60
Purchase #4	$189.87	12.665%	$213.917	$213.92	$213.90	$213.90
Purchase #5	$193.46	8.173%	$209.2715	$209.27	$209.25	$209.30
Purchase #6	$91.35	5.725%	$96.5798	$96.58	$96.60	$96.60
Purchase #7	$31.42	9.827%	$34.5076	$34.51	$34.50	$34.50
7 purchase totals =	$961.01		$1,057.9911	$1,058.00	$1,057.95	$1,058.10