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	$100.68	3.696%	$104.4011	$104.40	$104.40	$104.40
Purchase #2	$67.52	7.444%	$72.5462	$72.55	$72.55	$72.50
Purchase #3	$236.38	7.606%	$254.3591	$254.36	$254.35	$254.40
Purchase #4	$106.86	3.575%	$110.6802	$110.68	$110.70	$110.70
Purchase #5	$238.29	9.456%	$260.8227	$260.82	$260.80	$260.80
Purchase #6	$64.90	8.795%	$70.608	$70.61	$70.60	$70.60
Purchase #7	$119.67	9.827%	$131.43	$131.43	$131.45	$131.40
7 purchase totals =	$934.30		$1,004.8473	$1,004.85	$1,004.85	$1,004.80