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	$213.57	10.428%	$235.8411	$235.84	$235.85	$235.80
Purchase #2	$209.68	4.638%	$219.405	$219.41	$219.40	$219.40
Purchase #3	$51.29	12.556%	$57.73	$57.73	$57.75	$57.70
Purchase #4	$92.43	7.641%	$99.4926	$99.49	$99.50	$99.50
Purchase #5	$91.38	9.679%	$100.2247	$100.22	$100.20	$100.20
Purchase #6	$71.79	9.151%	$78.3595	$78.36	$78.35	$78.40
Purchase #7	$151.54	4.580%	$158.4805	$158.48	$158.50	$158.50
7 purchase totals =	$881.68		$949.5334	$949.53	$949.55	$949.50