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	$200.77	10.870%	$222.5937	$222.59	$222.60	$222.60
Purchase #2	$203.36	9.709%	$223.1042	$223.10	$223.10	$223.10
Purchase #3	$195.99	12.122%	$219.7479	$219.75	$219.75	$219.70
Purchase #4	$103.33	5.765%	$109.287	$109.29	$109.30	$109.30
Purchase #5	$90.29	11.332%	$100.5217	$100.52	$100.50	$100.50
Purchase #6	$171.99	10.605%	$190.2295	$190.23	$190.25	$190.20
Purchase #7	$158.90	13.510%	$180.3674	$180.37	$180.35	$180.40
7 purchase totals =	$1,124.63		$1,245.8514	$1,245.85	$1,245.85	$1,245.80