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	$218.31	10.796%	$241.8787	$241.88	$241.90	$241.90
Purchase #2	$36.39	9.457%	$39.8314	$39.83	$39.85	$39.80
Purchase #3	$78.43	5.799%	$82.9782	$82.98	$83.00	$83.00
Purchase #4	$237.91	12.811%	$268.3887	$268.39	$268.40	$268.40
Purchase #5	$86.91	9.442%	$95.116	$95.12	$95.10	$95.10
Purchase #6	$131.95	7.733%	$142.1537	$142.15	$142.15	$142.20
Purchase #7	$68.66	13.845%	$78.166	$78.17	$78.15	$78.20
7 purchase totals =	$858.56		$948.5127	$948.52	$948.55	$948.60