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	$175.64	11.820%	$196.4006	$196.40	$196.40	$196.40
Purchase #2	$63.70	13.528%	$72.3173	$72.32	$72.30	$72.30
Purchase #3	$81.42	9.116%	$88.8422	$88.84	$88.85	$88.80
Purchase #4	$32.97	3.567%	$34.146	$34.15	$34.15	$34.10
Purchase #5	$57.39	3.675%	$59.4991	$59.50	$59.50	$59.50
Purchase #6	$239.83	12.364%	$269.4826	$269.48	$269.50	$269.50
Purchase #7	$244.39	6.628%	$260.5882	$260.59	$260.60	$260.60
7 purchase totals =	$895.34		$981.2760	$981.28	$981.30	$981.20