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	$87.46	5.767%	$92.5038	$92.50	$92.50	$92.50
Purchase #2	$99.93	10.619%	$110.5416	$110.54	$110.55	$110.50
Purchase #3	$97.48	11.342%	$108.5362	$108.54	$108.55	$108.50
Purchase #4	$247.77	8.355%	$268.4712	$268.47	$268.45	$268.50
Purchase #5	$240.76	11.330%	$268.0381	$268.04	$268.05	$268.00
Purchase #6	$55.37	11.646%	$61.8184	$61.82	$61.80	$61.80
Purchase #7	$207.55	6.698%	$221.4517	$221.45	$221.45	$221.50
7 purchase totals =	$1,036.32		$1,131.3610	$1,131.36	$1,131.35	$1,131.30