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	$167.91	10.355%	$185.2971	$185.30	$185.30	$185.30
Purchase #2	$188.40	5.567%	$198.8882	$198.89	$198.90	$198.90
Purchase #3	$187.77	13.732%	$213.5546	$213.55	$213.55	$213.60
Purchase #4	$14.56	8.553%	$15.8053	$15.81	$15.80	$15.80
Purchase #5	$196.61	12.612%	$221.4065	$221.41	$221.40	$221.40
Purchase #6	$212.98	10.311%	$234.9404	$234.94	$234.95	$234.90
Purchase #7	$200.59	12.376%	$225.415	$225.42	$225.40	$225.40
7 purchase totals =	$1,168.82		$1,295.3071	$1,295.32	$1,295.30	$1,295.30