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	$94.29	11.245%	$104.8929	$104.89	$104.90	$104.90
Purchase #2	$209.62	11.473%	$233.6697	$233.67	$233.65	$233.70
Purchase #3	$225.76	12.367%	$253.6797	$253.68	$253.70	$253.70
Purchase #4	$88.48	13.700%	$100.6018	$100.60	$100.60	$100.60
Purchase #5	$32.67	3.593%	$33.8438	$33.84	$33.85	$33.80
Purchase #6	$111.91	10.354%	$123.4972	$123.50	$123.50	$123.50
Purchase #7	$86.72	7.109%	$92.8849	$92.88	$92.90	$92.90
7 purchase totals =	$849.45		$943.0700	$943.06	$943.10	$943.10