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	$94.35	6.135%	$100.1384	$100.14	$100.15	$100.10
Purchase #2	$101.63	3.751%	$105.4421	$105.44	$105.45	$105.40
Purchase #3	$65.93	7.561%	$70.915	$70.92	$70.90	$70.90
Purchase #4	$103.74	9.310%	$113.3982	$113.40	$113.40	$113.40
Purchase #5	$29.69	7.388%	$31.8835	$31.88	$31.90	$31.90
Purchase #6	$41.95	3.645%	$43.4791	$43.48	$43.50	$43.50
Purchase #7	$235.51	12.177%	$264.1881	$264.19	$264.20	$264.20
7 purchase totals =	$672.80		$729.4444	$729.45	$729.50	$729.40