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	$191.57	6.536%	$204.091	$204.09	$204.10	$204.10
Purchase #2	$80.86	9.404%	$88.4641	$88.46	$88.45	$88.50
Purchase #3	$229.77	3.189%	$237.0974	$237.10	$237.10	$237.10
Purchase #4	$82.78	6.283%	$87.9811	$87.98	$88.00	$88.00
Purchase #5	$30.49	6.672%	$32.5243	$32.52	$32.50	$32.50
Purchase #6	$96.87	12.605%	$109.0805	$109.08	$109.10	$109.10
Purchase #7	$28.84	11.309%	$32.1015	$32.10	$32.10	$32.10
7 purchase totals =	$741.18		$791.3399	$791.33	$791.35	$791.40