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	$179.32	7.300%	$192.4104	$192.41	$192.40	$192.40
Purchase #2	$96.99	3.426%	$100.3129	$100.31	$100.30	$100.30
Purchase #3	$136.29	5.227%	$143.4139	$143.41	$143.40	$143.40
Purchase #4	$199.84	9.214%	$218.2533	$218.25	$218.25	$218.30
Purchase #5	$229.56	11.719%	$256.4621	$256.46	$256.45	$256.50
Purchase #6	$41.91	7.668%	$45.1237	$45.12	$45.10	$45.10
Purchase #7	$72.48	8.634%	$78.7379	$78.74	$78.75	$78.70
7 purchase totals =	$956.39		$1,034.7142	$1,034.70	$1,034.65	$1,034.70