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	$105.49	5.605%	$111.4027	$111.40	$111.40	$111.40
Purchase #2	$46.29	10.422%	$51.1143	$51.11	$51.10	$51.10
Purchase #3	$181.66	3.790%	$188.5449	$188.54	$188.55	$188.50
Purchase #4	$9.32	10.796%	$10.3262	$10.33	$10.35	$10.30
Purchase #5	$182.35	7.115%	$195.3242	$195.32	$195.30	$195.30
Purchase #6	$148.92	12.615%	$167.7063	$167.71	$167.70	$167.70
Purchase #7	$112.60	9.358%	$123.1371	$123.14	$123.15	$123.10
7 purchase totals =	$786.63		$847.5557	$847.55	$847.55	$847.40