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	$12.77	8.595%	$13.8676	$13.87	$13.85	$13.90
Purchase #2	$41.92	3.791%	$43.5092	$43.51	$43.50	$43.50
Purchase #3	$151.46	4.600%	$158.4272	$158.43	$158.45	$158.40
Purchase #4	$250.63	6.375%	$266.6077	$266.61	$266.60	$266.60
Purchase #5	$115.56	10.560%	$127.7631	$127.76	$127.75	$127.80
Purchase #6	$246.94	8.515%	$267.9669	$267.97	$267.95	$268.00
Purchase #7	$186.50	11.449%	$207.8524	$207.85	$207.85	$207.90
7 purchase totals =	$1,005.78		$1,085.9941	$1,086.00	$1,085.95	$1,086.10