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	$104.78	7.666%	$112.8124	$112.81	$112.80	$112.80
Purchase #2	$233.80	11.871%	$261.5544	$261.55	$261.55	$261.60
Purchase #3	$185.54	13.115%	$209.8736	$209.87	$209.85	$209.90
Purchase #4	$195.52	11.247%	$217.5101	$217.51	$217.50	$217.50
Purchase #5	$240.90	5.180%	$253.3786	$253.38	$253.40	$253.40
Purchase #6	$120.73	5.485%	$127.352	$127.35	$127.35	$127.40
Purchase #7	$42.95	8.728%	$46.6987	$46.70	$46.70	$46.70
7 purchase totals =	$1,124.22		$1,229.1798	$1,229.17	$1,229.15	$1,229.30