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	$225.47	13.766%	$256.5082	$256.51	$256.50	$256.50
Purchase #2	$147.71	10.194%	$162.7676	$162.77	$162.75	$162.80
Purchase #3	$111.53	7.229%	$119.5925	$119.59	$119.60	$119.60
Purchase #4	$65.27	3.669%	$67.6648	$67.66	$67.65	$67.70
Purchase #5	$186.47	13.478%	$211.6024	$211.60	$211.60	$211.60
Purchase #6	$213.26	3.769%	$221.2978	$221.30	$221.30	$221.30
Purchase #7	$197.37	6.608%	$210.4122	$210.41	$210.40	$210.40
7 purchase totals =	$1,147.08		$1,249.8455	$1,249.84	$1,249.80	$1,249.90