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	$113.65	4.509%	$118.7745	$118.77	$118.75	$118.80
Purchase #2	$128.61	13.786%	$146.3402	$146.34	$146.35	$146.30
Purchase #3	$195.65	9.460%	$214.1585	$214.16	$214.15	$214.20
Purchase #4	$96.93	7.169%	$103.8789	$103.88	$103.90	$103.90
Purchase #5	$122.45	12.791%	$138.1126	$138.11	$138.10	$138.10
Purchase #6	$178.40	4.154%	$185.8107	$185.81	$185.80	$185.80
Purchase #7	$172.28	12.316%	$193.498	$193.50	$193.50	$193.50
7 purchase totals =	$1,007.97		$1,100.5734	$1,100.57	$1,100.55	$1,100.60