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	$233.57	11.463%	$260.3441	$260.34	$260.35	$260.30
Purchase #2	$91.87	5.102%	$96.5572	$96.56	$96.55	$96.60
Purchase #3	$49.57	12.156%	$55.5957	$55.60	$55.60	$55.60
Purchase #4	$187.72	4.825%	$196.7775	$196.78	$196.80	$196.80
Purchase #5	$143.90	3.243%	$148.5667	$148.57	$148.55	$148.60
Purchase #6	$178.85	6.599%	$190.6523	$190.65	$190.65	$190.70
Purchase #7	$61.42	4.619%	$64.257	$64.26	$64.25	$64.30
7 purchase totals =	$946.90		$1,012.7505	$1,012.76	$1,012.75	$1,012.90