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	$97.55	9.471%	$106.789	$106.79	$106.80	$106.80
Purchase #2	$229.43	11.375%	$255.5277	$255.53	$255.55	$255.50
Purchase #3	$87.25	4.868%	$91.4973	$91.50	$91.50	$91.50
Purchase #4	$63.99	8.450%	$69.3972	$69.40	$69.40	$69.40
Purchase #5	$50.85	6.409%	$54.109	$54.11	$54.10	$54.10
Purchase #6	$204.73	8.139%	$221.393	$221.39	$221.40	$221.40
Purchase #7	$69.96	4.138%	$72.8549	$72.85	$72.85	$72.90
7 purchase totals =	$803.76		$871.5681	$871.57	$871.60	$871.60