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	$133.39	8.660%	$144.9416	$144.94	$144.95	$144.90
Purchase #2	$111.84	13.557%	$127.0021	$127.00	$127.00	$127.00
Purchase #3	$109.43	9.360%	$119.6726	$119.67	$119.65	$119.70
Purchase #4	$119.63	12.648%	$134.7608	$134.76	$134.75	$134.80
Purchase #5	$185.60	7.469%	$199.4625	$199.46	$199.45	$199.50
Purchase #6	$89.53	13.561%	$101.6712	$101.67	$101.65	$101.70
Purchase #7	$228.61	6.480%	$243.4239	$243.42	$243.40	$243.40
7 purchase totals =	$978.03		$1,070.9347	$1,070.92	$1,070.85	$1,071.00