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	$92.60	11.404%	$103.1601	$103.16	$103.15	$103.20
Purchase #2	$151.58	8.738%	$164.8251	$164.83	$164.85	$164.80
Purchase #3	$187.54	9.250%	$204.8875	$204.89	$204.90	$204.90
Purchase #4	$165.56	12.357%	$186.0182	$186.02	$186.00	$186.00
Purchase #5	$37.85	4.146%	$39.4193	$39.42	$39.40	$39.40
Purchase #6	$111.52	12.438%	$125.3909	$125.39	$125.40	$125.40
Purchase #7	$206.31	5.247%	$217.1351	$217.14	$217.15	$217.10
7 purchase totals =	$952.96		$1,040.8362	$1,040.85	$1,040.85	$1,040.80