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	$122.96	3.605%	$127.3927	$127.39	$127.40	$127.40
Purchase #2	$193.84	5.552%	$204.602	$204.60	$204.60	$204.60
Purchase #3	$188.86	12.815%	$213.0624	$213.06	$213.05	$213.10
Purchase #4	$210.61	13.380%	$238.7896	$238.79	$238.80	$238.80
Purchase #5	$217.96	7.712%	$234.7691	$234.77	$234.75	$234.80
Purchase #6	$95.70	13.143%	$108.2779	$108.28	$108.30	$108.30
Purchase #7	$120.36	9.222%	$131.4596	$131.46	$131.45	$131.50
7 purchase totals =	$1,150.29		$1,258.3533	$1,258.35	$1,258.35	$1,258.50