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	$118.65	7.186%	$127.1762	$127.18	$127.20	$127.20
Purchase #2	$39.63	3.231%	$40.9104	$40.91	$40.90	$40.90
Purchase #3	$41.63	11.164%	$46.2776	$46.28	$46.30	$46.30
Purchase #4	$67.65	9.837%	$74.3047	$74.30	$74.30	$74.30
Purchase #5	$130.61	10.382%	$144.1699	$144.17	$144.15	$144.20
Purchase #6	$173.40	6.155%	$184.0728	$184.07	$184.05	$184.10
Purchase #7	$189.88	5.778%	$200.8513	$200.85	$200.85	$200.90
7 purchase totals =	$761.45		$817.7629	$817.76	$817.75	$817.90