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	$142.84	8.717%	$155.2914	$155.29	$155.30	$155.30
Purchase #2	$63.78	11.355%	$71.0222	$71.02	$71.00	$71.00
Purchase #3	$89.57	3.563%	$92.7614	$92.76	$92.75	$92.80
Purchase #4	$152.32	10.553%	$168.3943	$168.39	$168.40	$168.40
Purchase #5	$226.78	8.484%	$246.02	$246.02	$246.00	$246.00
Purchase #6	$124.42	13.374%	$141.0599	$141.06	$141.05	$141.10
Purchase #7	$82.93	8.548%	$90.0189	$90.02	$90.00	$90.00
7 purchase totals =	$882.64		$964.5681	$964.56	$964.50	$964.60