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	$62.37	7.629%	$67.1282	$67.13	$67.15	$67.10
Purchase #2	$146.29	12.739%	$164.9259	$164.93	$164.95	$164.90
Purchase #3	$189.73	11.288%	$211.1467	$211.15	$211.15	$211.10
Purchase #4	$143.74	6.109%	$152.5211	$152.52	$152.50	$152.50
Purchase #5	$212.65	13.127%	$240.5646	$240.56	$240.55	$240.60
Purchase #6	$73.38	10.262%	$80.9103	$80.91	$80.90	$80.90
Purchase #7	$92.97	4.606%	$97.2522	$97.25	$97.25	$97.30
7 purchase totals =	$921.13		$1,014.4490	$1,014.45	$1,014.45	$1,014.40