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	$176.53	11.459%	$196.7586	$196.76	$196.75	$196.80
Purchase #2	$162.89	3.653%	$168.8404	$168.84	$168.85	$168.80
Purchase #3	$34.74	9.643%	$38.09	$38.09	$38.10	$38.10
Purchase #4	$118.63	12.170%	$133.0673	$133.07	$133.05	$133.10
Purchase #5	$47.90	4.625%	$50.1154	$50.12	$50.10	$50.10
Purchase #6	$76.71	11.828%	$85.7833	$85.78	$85.80	$85.80
Purchase #7	$239.55	12.473%	$269.4291	$269.43	$269.45	$269.40
7 purchase totals =	$856.95		$942.0841	$942.09	$942.10	$942.10