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	$86.38	13.802%	$98.3022	$98.30	$98.30	$98.30
Purchase #2	$108.81	13.126%	$123.0924	$123.09	$123.10	$123.10
Purchase #3	$109.89	13.471%	$124.6933	$124.69	$124.70	$124.70
Purchase #4	$67.77	6.449%	$72.1405	$72.14	$72.15	$72.10
Purchase #5	$72.75	11.421%	$81.0588	$81.06	$81.05	$81.10
Purchase #6	$161.48	7.762%	$174.0141	$174.01	$174.00	$174.00
Purchase #7	$201.42	13.461%	$228.5331	$228.53	$228.55	$228.50
7 purchase totals =	$808.50		$901.8344	$901.82	$901.85	$901.80