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	$74.60	12.246%	$83.7355	$83.74	$83.75	$83.70
Purchase #2	$209.50	4.588%	$219.1119	$219.11	$219.10	$219.10
Purchase #3	$86.46	4.716%	$90.5375	$90.54	$90.55	$90.50
Purchase #4	$171.47	8.704%	$186.3947	$186.39	$186.40	$186.40
Purchase #5	$100.38	11.124%	$111.5463	$111.55	$111.55	$111.50
Purchase #6	$114.47	10.832%	$126.8694	$126.87	$126.85	$126.90
Purchase #7	$245.57	12.638%	$276.6051	$276.61	$276.60	$276.60
7 purchase totals =	$1,002.45		$1,094.8004	$1,094.81	$1,094.80	$1,094.70