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	$218.91	7.707%	$235.7814	$235.78	$235.80	$235.80
Purchase #2	$169.41	12.334%	$190.305	$190.31	$190.30	$190.30
Purchase #3	$193.56	4.124%	$201.5424	$201.54	$201.55	$201.50
Purchase #4	$167.87	8.352%	$181.8905	$181.89	$181.90	$181.90
Purchase #5	$41.99	4.432%	$43.851	$43.85	$43.85	$43.90
Purchase #6	$10.40	4.152%	$10.8318	$10.83	$10.85	$10.80
Purchase #7	$139.57	11.496%	$155.615	$155.62	$155.60	$155.60
7 purchase totals =	$941.71		$1,019.8171	$1,019.82	$1,019.85	$1,019.80