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	$246.41	7.125%	$263.9667	$263.97	$263.95	$264.00
Purchase #2	$214.40	12.827%	$241.9011	$241.90	$241.90	$241.90
Purchase #3	$6.59	7.429%	$7.0796	$7.08	$7.10	$7.10
Purchase #4	$90.93	10.563%	$100.5349	$100.53	$100.55	$100.50
Purchase #5	$110.46	12.404%	$124.1615	$124.16	$124.15	$124.20
Purchase #6	$119.60	11.624%	$133.5023	$133.50	$133.50	$133.50
Purchase #7	$161.71	10.855%	$179.2636	$179.26	$179.25	$179.30
7 purchase totals =	$950.10		$1,050.4097	$1,050.40	$1,050.40	$1,050.50