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	$157.83	4.346%	$164.6893	$164.69	$164.70	$164.70
Purchase #2	$117.27	4.323%	$122.3396	$122.34	$122.35	$122.30
Purchase #3	$6.41	11.846%	$7.1693	$7.17	$7.15	$7.20
Purchase #4	$106.33	12.215%	$119.3182	$119.32	$119.30	$119.30
Purchase #5	$238.73	7.136%	$255.7658	$255.77	$255.75	$255.80
Purchase #6	$81.73	13.344%	$92.6361	$92.64	$92.65	$92.60
Purchase #7	$177.88	10.604%	$196.7424	$196.74	$196.75	$196.70
7 purchase totals =	$886.18		$958.6607	$958.67	$958.65	$958.60