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	$177.84	11.455%	$198.2116	$198.21	$198.20	$198.20
Purchase #2	$213.83	9.246%	$233.6007	$233.60	$233.60	$233.60
Purchase #3	$52.46	9.711%	$57.5544	$57.55	$57.55	$57.60
Purchase #4	$127.89	6.667%	$136.4164	$136.42	$136.40	$136.40
Purchase #5	$59.70	5.274%	$62.8486	$62.85	$62.85	$62.80
Purchase #6	$227.40	6.410%	$241.9763	$241.98	$242.00	$242.00
Purchase #7	$152.74	4.516%	$159.6377	$159.64	$159.65	$159.60
7 purchase totals =	$1,011.86		$1,090.2457	$1,090.25	$1,090.25	$1,090.20