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	$56.32	9.356%	$61.5893	$61.59	$61.60	$61.60
Purchase #2	$44.42	6.846%	$47.461	$47.46	$47.45	$47.50
Purchase #3	$136.43	6.631%	$145.4767	$145.48	$145.50	$145.50
Purchase #4	$185.39	13.814%	$210.9998	$211.00	$211.00	$211.00
Purchase #5	$141.87	6.179%	$150.6361	$150.64	$150.65	$150.60
Purchase #6	$88.35	7.823%	$95.2616	$95.26	$95.25	$95.30
Purchase #7	$127.39	4.276%	$132.8372	$132.84	$132.85	$132.80
7 purchase totals =	$780.17		$844.2617	$844.27	$844.30	$844.30