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	$156.40	3.158%	$161.3391	$161.34	$161.35	$161.30
Purchase #2	$74.98	4.790%	$78.5715	$78.57	$78.55	$78.60
Purchase #3	$217.49	9.567%	$238.2973	$238.30	$238.30	$238.30
Purchase #4	$67.75	6.171%	$71.9309	$71.93	$71.95	$71.90
Purchase #5	$28.63	12.757%	$32.2823	$32.28	$32.30	$32.30
Purchase #6	$199.80	6.841%	$213.4683	$213.47	$213.45	$213.50
Purchase #7	$64.85	3.424%	$67.0705	$67.07	$67.05	$67.10
7 purchase totals =	$809.90		$862.9599	$862.96	$862.95	$863.00