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	$198.39	13.692%	$225.5536	$225.55	$225.55	$225.60
Purchase #2	$144.78	5.751%	$153.1063	$153.11	$153.10	$153.10
Purchase #3	$15.97	5.666%	$16.8749	$16.87	$16.85	$16.90
Purchase #4	$229.70	11.367%	$255.81	$255.81	$255.80	$255.80
Purchase #5	$14.47	8.862%	$15.7523	$15.75	$15.75	$15.80
Purchase #6	$249.71	6.333%	$265.5241	$265.52	$265.50	$265.50
Purchase #7	$245.57	4.168%	$255.8054	$255.81	$255.80	$255.80
7 purchase totals =	$1,098.59		$1,188.4266	$1,188.42	$1,188.35	$1,188.50