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	$119.65	8.682%	$130.038	$130.04	$130.05	$130.00
Purchase #2	$189.69	11.508%	$211.5195	$211.52	$211.50	$211.50
Purchase #3	$211.71	9.239%	$231.2699	$231.27	$231.25	$231.30
Purchase #4	$173.65	6.801%	$185.4599	$185.46	$185.45	$185.50
Purchase #5	$249.59	8.786%	$271.519	$271.52	$271.50	$271.50
Purchase #6	$43.27	7.475%	$46.5044	$46.50	$46.50	$46.50
Purchase #7	$131.97	8.237%	$142.8404	$142.84	$142.85	$142.80
7 purchase totals =	$1,119.53		$1,219.1511	$1,219.15	$1,219.10	$1,219.10