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	$95.47	4.286%	$99.5618	$99.56	$99.55	$99.60
Purchase #2	$222.46	11.581%	$248.2231	$248.22	$248.20	$248.20
Purchase #3	$53.97	13.509%	$61.2608	$61.26	$61.25	$61.30
Purchase #4	$118.35	5.683%	$125.0758	$125.08	$125.10	$125.10
Purchase #5	$216.70	6.382%	$230.5298	$230.53	$230.55	$230.50
Purchase #6	$164.77	4.524%	$172.2242	$172.22	$172.20	$172.20
Purchase #7	$224.61	8.166%	$242.9517	$242.95	$242.95	$243.00
7 purchase totals =	$1,096.33		$1,179.8272	$1,179.82	$1,179.80	$1,179.90