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	$172.35	4.114%	$179.4405	$179.44	$179.45	$179.40
Purchase #2	$8.57	3.859%	$8.9007	$8.90	$8.90	$8.90
Purchase #3	$179.51	10.555%	$198.4573	$198.46	$198.45	$198.50
Purchase #4	$240.34	9.619%	$263.4583	$263.46	$263.45	$263.50
Purchase #5	$238.98	9.394%	$261.4298	$261.43	$261.45	$261.40
Purchase #6	$179.99	6.768%	$192.1717	$192.17	$192.15	$192.20
Purchase #7	$88.62	4.361%	$92.4847	$92.48	$92.50	$92.50
7 purchase totals =	$1,108.36		$1,196.3430	$1,196.34	$1,196.35	$1,196.40