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	$202.52	10.513%	$223.8109	$223.81	$223.80	$223.80
Purchase #2	$146.69	12.580%	$165.1436	$165.14	$165.15	$165.10
Purchase #3	$187.38	10.380%	$206.83	$206.83	$206.85	$206.80
Purchase #4	$96.44	12.150%	$108.1575	$108.16	$108.15	$108.20
Purchase #5	$50.50	7.304%	$54.1885	$54.19	$54.20	$54.20
Purchase #6	$56.60	12.215%	$63.5137	$63.51	$63.50	$63.50
Purchase #7	$173.88	7.106%	$186.2359	$186.24	$186.25	$186.20
7 purchase totals =	$914.01		$1,007.8801	$1,007.88	$1,007.90	$1,007.80