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	$70.95	10.516%	$78.4111	$78.41	$78.40	$78.40
Purchase #2	$218.93	8.732%	$238.047	$238.05	$238.05	$238.00
Purchase #3	$131.75	7.423%	$141.5298	$141.53	$141.55	$141.50
Purchase #4	$195.85	7.666%	$210.8639	$210.86	$210.85	$210.90
Purchase #5	$202.47	5.754%	$214.1201	$214.12	$214.10	$214.10
Purchase #6	$189.60	3.864%	$196.9261	$196.93	$196.95	$196.90
Purchase #7	$83.93	6.161%	$89.1009	$89.10	$89.10	$89.10
7 purchase totals =	$1,093.48		$1,168.9989	$1,169.00	$1,169.00	$1,168.90