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	$116.44	10.407%	$128.5579	$128.56	$128.55	$128.60
Purchase #2	$184.79	13.581%	$209.8863	$209.89	$209.90	$209.90
Purchase #3	$141.51	3.581%	$146.5775	$146.58	$146.60	$146.60
Purchase #4	$120.99	11.218%	$134.5627	$134.56	$134.55	$134.60
Purchase #5	$92.35	7.830%	$99.581	$99.58	$99.60	$99.60
Purchase #6	$244.57	3.797%	$253.8563	$253.86	$253.85	$253.90
Purchase #7	$123.93	13.166%	$140.2466	$140.25	$140.25	$140.20
7 purchase totals =	$1,024.58		$1,113.2683	$1,113.28	$1,113.30	$1,113.40