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	$189.43	6.483%	$201.7107	$201.71	$201.70	$201.70
Purchase #2	$52.97	8.486%	$57.465	$57.47	$57.45	$57.50
Purchase #3	$116.46	9.616%	$127.6588	$127.66	$127.65	$127.70
Purchase #4	$174.43	6.401%	$185.5953	$185.60	$185.60	$185.60
Purchase #5	$200.96	7.113%	$215.2543	$215.25	$215.25	$215.30
Purchase #6	$193.75	11.184%	$215.419	$215.42	$215.40	$215.40
Purchase #7	$19.46	5.674%	$20.5642	$20.56	$20.55	$20.60
7 purchase totals =	$947.46		$1,023.6673	$1,023.67	$1,023.60	$1,023.80