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	$51.26	3.361%	$52.9828	$52.98	$53.00	$53.00
Purchase #2	$52.63	13.861%	$59.925	$59.93	$59.95	$59.90
Purchase #3	$205.32	3.573%	$212.6561	$212.66	$212.65	$212.70
Purchase #4	$243.59	5.750%	$257.5964	$257.60	$257.60	$257.60
Purchase #5	$27.71	7.720%	$29.8492	$29.85	$29.85	$29.80
Purchase #6	$109.57	9.159%	$119.6055	$119.61	$119.60	$119.60
Purchase #7	$32.45	9.717%	$35.6032	$35.60	$35.60	$35.60
7 purchase totals =	$722.53		$768.2182	$768.23	$768.25	$768.20