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	$90.46	9.287%	$98.861	$98.86	$98.85	$98.90
Purchase #2	$245.96	3.700%	$255.0605	$255.06	$255.05	$255.10
Purchase #3	$177.51	12.611%	$199.8958	$199.90	$199.90	$199.90
Purchase #4	$65.45	8.256%	$70.8536	$70.85	$70.85	$70.90
Purchase #5	$79.75	8.601%	$86.6093	$86.61	$86.60	$86.60
Purchase #6	$152.96	13.623%	$173.7977	$173.80	$173.80	$173.80
Purchase #7	$181.71	9.112%	$198.2674	$198.27	$198.25	$198.30
7 purchase totals =	$993.80		$1,083.3453	$1,083.35	$1,083.30	$1,083.50