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	$117.39	12.136%	$131.6365	$131.64	$131.65	$131.60
Purchase #2	$81.95	9.335%	$89.6	$89.60	$89.60	$89.60
Purchase #3	$218.46	9.572%	$239.371	$239.37	$239.35	$239.40
Purchase #4	$211.60	7.770%	$228.0413	$228.04	$228.05	$228.00
Purchase #5	$127.63	3.607%	$132.2336	$132.23	$132.25	$132.20
Purchase #6	$229.94	9.779%	$252.4258	$252.43	$252.45	$252.40
Purchase #7	$56.62	4.608%	$59.229	$59.23	$59.25	$59.20
7 purchase totals =	$1,043.59		$1,132.5372	$1,132.54	$1,132.60	$1,132.40