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	$206.63	13.799%	$235.1429	$235.14	$235.15	$235.10
Purchase #2	$135.28	12.275%	$151.8856	$151.89	$151.90	$151.90
Purchase #3	$208.52	5.336%	$219.6466	$219.65	$219.65	$219.60
Purchase #4	$151.68	9.812%	$166.5628	$166.56	$166.55	$166.60
Purchase #5	$79.46	6.744%	$84.8188	$84.82	$84.80	$84.80
Purchase #6	$46.53	4.284%	$48.5233	$48.52	$48.50	$48.50
Purchase #7	$233.51	3.222%	$241.0337	$241.03	$241.05	$241.00
7 purchase totals =	$1,061.61		$1,147.6137	$1,147.61	$1,147.60	$1,147.50