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	$114.77	11.136%	$127.5508	$127.55	$127.55	$127.60
Purchase #2	$72.54	12.747%	$81.7867	$81.79	$81.80	$81.80
Purchase #3	$204.50	5.692%	$216.1401	$216.14	$216.15	$216.10
Purchase #4	$217.48	8.434%	$235.8223	$235.82	$235.80	$235.80
Purchase #5	$147.98	8.677%	$160.8202	$160.82	$160.80	$160.80
Purchase #6	$85.65	10.256%	$94.4343	$94.43	$94.45	$94.40
Purchase #7	$205.91	13.789%	$234.3029	$234.30	$234.30	$234.30
7 purchase totals =	$1,048.83		$1,150.8573	$1,150.85	$1,150.85	$1,150.80