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	$48.97	13.177%	$55.4228	$55.42	$55.40	$55.40
Purchase #2	$98.93	10.740%	$109.5551	$109.56	$109.55	$109.60
Purchase #3	$209.39	11.439%	$233.3421	$233.34	$233.35	$233.30
Purchase #4	$111.36	10.576%	$123.1374	$123.14	$123.15	$123.10
Purchase #5	$237.77	7.633%	$255.919	$255.92	$255.90	$255.90
Purchase #6	$207.57	3.483%	$214.7997	$214.80	$214.80	$214.80
Purchase #7	$155.57	7.862%	$167.8009	$167.80	$167.80	$167.80
7 purchase totals =	$1,069.56		$1,159.9770	$1,159.98	$1,159.95	$1,159.90