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	$225.62	7.503%	$242.5483	$242.55	$242.55	$242.50
Purchase #2	$126.79	9.572%	$138.9263	$138.93	$138.95	$138.90
Purchase #3	$61.80	9.698%	$67.7934	$67.79	$67.80	$67.80
Purchase #4	$156.54	12.112%	$175.5001	$175.50	$175.50	$175.50
Purchase #5	$77.87	5.254%	$81.9613	$81.96	$81.95	$82.00
Purchase #6	$91.96	9.648%	$100.8323	$100.83	$100.85	$100.80
Purchase #7	$102.34	3.290%	$105.707	$105.71	$105.70	$105.70
7 purchase totals =	$842.92		$913.2687	$913.27	$913.30	$913.20