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	$54.59	13.825%	$62.1371	$62.14	$62.15	$62.10
Purchase #2	$29.71	12.816%	$33.5176	$33.52	$33.50	$33.50
Purchase #3	$72.54	5.329%	$76.4057	$76.41	$76.40	$76.40
Purchase #4	$165.46	3.408%	$171.0989	$171.10	$171.10	$171.10
Purchase #5	$80.28	12.200%	$90.0742	$90.07	$90.05	$90.10
Purchase #6	$66.70	11.550%	$74.4039	$74.40	$74.40	$74.40
Purchase #7	$99.31	13.194%	$112.413	$112.41	$112.40	$112.40
7 purchase totals =	$568.59		$620.0504	$620.05	$620.00	$620.00