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	$96.72	6.290%	$102.8037	$102.80	$102.80	$102.80
Purchase #2	$226.56	7.185%	$242.8383	$242.84	$242.85	$242.80
Purchase #3	$236.32	3.120%	$243.6932	$243.69	$243.70	$243.70
Purchase #4	$17.30	12.602%	$19.4801	$19.48	$19.50	$19.50
Purchase #5	$54.80	13.406%	$62.1465	$62.15	$62.15	$62.10
Purchase #6	$38.32	10.388%	$42.3007	$42.30	$42.30	$42.30
Purchase #7	$205.94	6.628%	$219.5897	$219.59	$219.60	$219.60
7 purchase totals =	$875.96		$932.8522	$932.85	$932.90	$932.80