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	$62.97	6.839%	$67.2765	$67.28	$67.30	$67.30
Purchase #2	$209.96	8.457%	$227.7163	$227.72	$227.70	$227.70
Purchase #3	$216.74	7.611%	$233.2361	$233.24	$233.25	$233.20
Purchase #4	$187.42	9.371%	$204.9831	$204.98	$205.00	$205.00
Purchase #5	$130.58	5.543%	$137.818	$137.82	$137.80	$137.80
Purchase #6	$216.34	11.283%	$240.7496	$240.75	$240.75	$240.70
Purchase #7	$65.25	11.249%	$72.59	$72.59	$72.60	$72.60
7 purchase totals =	$1,089.26		$1,184.3696	$1,184.38	$1,184.40	$1,184.30