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	$75.29	13.271%	$85.2817	$85.28	$85.30	$85.30
Purchase #2	$173.79	3.787%	$180.3714	$180.37	$180.35	$180.40
Purchase #3	$30.81	5.325%	$32.4506	$32.45	$32.45	$32.50
Purchase #4	$246.97	8.741%	$268.5576	$268.56	$268.55	$268.60
Purchase #5	$244.62	4.600%	$255.8725	$255.87	$255.85	$255.90
Purchase #6	$82.84	7.615%	$89.1483	$89.15	$89.15	$89.10
Purchase #7	$168.32	10.524%	$186.034	$186.03	$186.05	$186.00
7 purchase totals =	$1,022.64		$1,097.7161	$1,097.71	$1,097.70	$1,097.80