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	$84.95	9.288%	$92.8402	$92.84	$92.85	$92.80
Purchase #2	$120.34	6.171%	$127.7662	$127.77	$127.75	$127.80
Purchase #3	$249.82	7.208%	$267.827	$267.83	$267.85	$267.80
Purchase #4	$146.89	5.845%	$155.4757	$155.48	$155.50	$155.50
Purchase #5	$73.87	12.118%	$82.8216	$82.82	$82.80	$82.80
Purchase #6	$55.43	8.440%	$60.1083	$60.11	$60.10	$60.10
Purchase #7	$248.75	9.714%	$272.9136	$272.91	$272.90	$272.90
7 purchase totals =	$980.05		$1,059.7526	$1,059.76	$1,059.75	$1,059.70