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	$113.27	10.696%	$125.3854	$125.39	$125.40	$125.40
Purchase #2	$140.85	5.688%	$148.8615	$148.86	$148.85	$148.90
Purchase #3	$229.41	13.250%	$259.8068	$259.81	$259.80	$259.80
Purchase #4	$39.25	6.796%	$41.9174	$41.92	$41.90	$41.90
Purchase #5	$209.54	4.297%	$218.5439	$218.54	$218.55	$218.50
Purchase #6	$96.85	6.242%	$102.8954	$102.90	$102.90	$102.90
Purchase #7	$35.61	13.578%	$40.4451	$40.45	$40.45	$40.40
7 purchase totals =	$864.78		$937.8555	$937.87	$937.85	$937.80