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	$215.86	11.698%	$241.1113	$241.11	$241.10	$241.10
Purchase #2	$101.46	7.810%	$109.384	$109.38	$109.40	$109.40
Purchase #3	$177.44	8.399%	$192.3432	$192.34	$192.35	$192.30
Purchase #4	$61.66	5.270%	$64.9095	$64.91	$64.90	$64.90
Purchase #5	$120.96	8.733%	$131.5234	$131.52	$131.50	$131.50
Purchase #6	$105.47	8.645%	$114.5879	$114.59	$114.60	$114.60
Purchase #7	$84.31	5.438%	$88.8948	$88.89	$88.90	$88.90
7 purchase totals =	$867.16		$942.7541	$942.74	$942.75	$942.70