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	$103.51	6.107%	$109.8314	$109.83	$109.85	$109.80
Purchase #2	$148.94	3.131%	$153.6033	$153.60	$153.60	$153.60
Purchase #3	$69.86	3.666%	$72.4211	$72.42	$72.40	$72.40
Purchase #4	$37.25	4.230%	$38.8257	$38.83	$38.85	$38.80
Purchase #5	$186.98	13.307%	$211.8614	$211.86	$211.85	$211.90
Purchase #6	$103.36	4.662%	$108.1786	$108.18	$108.20	$108.20
Purchase #7	$207.67	5.306%	$218.689	$218.69	$218.70	$218.70
7 purchase totals =	$857.57		$913.4105	$913.41	$913.45	$913.40