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	$187.69	5.150%	$197.356	$197.36	$197.35	$197.40
Purchase #2	$98.67	7.338%	$105.9104	$105.91	$105.90	$105.90
Purchase #3	$124.60	4.367%	$130.0413	$130.04	$130.05	$130.00
Purchase #4	$84.90	7.785%	$91.5095	$91.51	$91.50	$91.50
Purchase #5	$73.55	13.632%	$83.5763	$83.58	$83.60	$83.60
Purchase #6	$158.52	4.357%	$165.4267	$165.43	$165.45	$165.40
Purchase #7	$103.64	9.506%	$113.492	$113.49	$113.50	$113.50
7 purchase totals =	$831.57		$887.3122	$887.32	$887.35	$887.30