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	$96.61	7.283%	$103.6461	$103.65	$103.65	$103.60
Purchase #2	$97.93	11.797%	$109.4828	$109.48	$109.50	$109.50
Purchase #3	$60.66	11.529%	$67.6535	$67.65	$67.65	$67.70
Purchase #4	$83.30	7.274%	$89.3592	$89.36	$89.35	$89.40
Purchase #5	$213.48	12.717%	$240.6283	$240.63	$240.65	$240.60
Purchase #6	$14.64	8.330%	$15.8595	$15.86	$15.85	$15.90
Purchase #7	$221.41	3.402%	$228.9424	$228.94	$228.95	$228.90
7 purchase totals =	$788.03		$855.5718	$855.57	$855.60	$855.60