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	$72.35	8.558%	$78.5417	$78.54	$78.55	$78.50
Purchase #2	$184.34	8.302%	$199.6439	$199.64	$199.65	$199.60
Purchase #3	$190.55	12.626%	$214.6088	$214.61	$214.60	$214.60
Purchase #4	$104.60	11.477%	$116.6049	$116.60	$116.60	$116.60
Purchase #5	$206.94	7.627%	$222.7233	$222.72	$222.70	$222.70
Purchase #6	$168.43	11.538%	$187.8635	$187.86	$187.85	$187.90
Purchase #7	$30.52	8.744%	$33.1887	$33.19	$33.20	$33.20
7 purchase totals =	$957.73		$1,053.1748	$1,053.16	$1,053.15	$1,053.10