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	$61.38	10.378%	$67.75	$67.75	$67.75	$67.80
Purchase #2	$180.44	3.412%	$186.5966	$186.60	$186.60	$186.60
Purchase #3	$213.65	5.591%	$225.5952	$225.60	$225.60	$225.60
Purchase #4	$143.54	9.159%	$156.6868	$156.69	$156.70	$156.70
Purchase #5	$15.71	11.642%	$17.539	$17.54	$17.55	$17.50
Purchase #6	$240.86	3.704%	$249.7815	$249.78	$249.80	$249.80
Purchase #7	$53.75	11.534%	$59.9495	$59.95	$59.95	$59.90
7 purchase totals =	$909.33		$963.8986	$963.91	$963.95	$963.90