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	$34.66	5.194%	$36.4602	$36.46	$36.45	$36.50
Purchase #2	$190.82	11.436%	$212.6422	$212.64	$212.65	$212.60
Purchase #3	$239.40	7.300%	$256.8762	$256.88	$256.90	$256.90
Purchase #4	$99.97	9.511%	$109.4781	$109.48	$109.50	$109.50
Purchase #5	$151.51	11.168%	$168.4306	$168.43	$168.45	$168.40
Purchase #6	$7.49	5.450%	$7.8982	$7.90	$7.90	$7.90
Purchase #7	$74.87	10.158%	$82.4753	$82.48	$82.50	$82.50
7 purchase totals =	$798.72		$874.2608	$874.27	$874.35	$874.30