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	$52.38	12.597%	$58.9783	$58.98	$59.00	$59.00
Purchase #2	$226.85	3.526%	$234.8487	$234.85	$234.85	$234.80
Purchase #3	$43.86	3.469%	$45.3815	$45.38	$45.40	$45.40
Purchase #4	$190.34	11.236%	$211.7266	$211.73	$211.75	$211.70
Purchase #5	$75.74	7.578%	$81.4796	$81.48	$81.50	$81.50
Purchase #6	$127.73	13.490%	$144.9608	$144.96	$144.95	$145.00
Purchase #7	$208.39	9.192%	$227.5452	$227.55	$227.55	$227.50
7 purchase totals =	$925.29		$1,004.9207	$1,004.93	$1,005.00	$1,004.90