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	$130.85	8.398%	$141.8388	$141.84	$141.85	$141.80
Purchase #2	$70.52	11.806%	$78.8456	$78.85	$78.85	$78.80
Purchase #3	$177.75	7.443%	$190.9799	$190.98	$191.00	$191.00
Purchase #4	$246.77	11.733%	$275.7235	$275.72	$275.70	$275.70
Purchase #5	$127.35	8.702%	$138.432	$138.43	$138.45	$138.40
Purchase #6	$39.93	4.581%	$41.7592	$41.76	$41.75	$41.80
Purchase #7	$163.69	11.602%	$182.6813	$182.68	$182.70	$182.70
7 purchase totals =	$956.86		$1,050.2603	$1,050.26	$1,050.30	$1,050.20