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	$110.33	4.124%	$114.88	$114.88	$114.90	$114.90
Purchase #2	$189.57	3.827%	$196.8248	$196.82	$196.80	$196.80
Purchase #3	$82.73	5.839%	$87.5606	$87.56	$87.55	$87.60
Purchase #4	$31.56	5.812%	$33.3943	$33.39	$33.40	$33.40
Purchase #5	$94.41	8.473%	$102.4094	$102.41	$102.40	$102.40
Purchase #6	$229.49	5.491%	$242.0913	$242.09	$242.10	$242.10
Purchase #7	$219.31	6.733%	$234.0761	$234.08	$234.10	$234.10
7 purchase totals =	$957.40		$1,011.2365	$1,011.23	$1,011.25	$1,011.30