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	$134.59	9.152%	$146.9077	$146.91	$146.90	$146.90
Purchase #2	$90.82	6.715%	$96.9186	$96.92	$96.90	$96.90
Purchase #3	$193.61	6.567%	$206.3244	$206.32	$206.30	$206.30
Purchase #4	$65.93	6.627%	$70.2992	$70.30	$70.30	$70.30
Purchase #5	$190.27	7.742%	$205.0007	$205.00	$205.00	$205.00
Purchase #6	$248.44	9.799%	$272.7846	$272.78	$272.80	$272.80
Purchase #7	$78.57	5.285%	$82.7224	$82.72	$82.70	$82.70
7 purchase totals =	$1,002.23		$1,080.9576	$1,080.95	$1,080.90	$1,080.90