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	$101.25	10.167%	$111.5441	$111.54	$111.55	$111.50
Purchase #2	$57.37	10.818%	$63.5763	$63.58	$63.60	$63.60
Purchase #3	$42.58	3.453%	$44.0503	$44.05	$44.05	$44.10
Purchase #4	$52.27	3.159%	$53.9212	$53.92	$53.90	$53.90
Purchase #5	$156.66	7.459%	$168.3453	$168.35	$168.35	$168.30
Purchase #6	$174.40	4.436%	$182.1364	$182.14	$182.15	$182.10
Purchase #7	$229.95	9.313%	$251.3652	$251.37	$251.35	$251.40
7 purchase totals =	$814.48		$874.9388	$874.95	$874.95	$874.90