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	$141.57	11.212%	$157.4428	$157.44	$157.45	$157.40
Purchase #2	$66.92	7.580%	$71.9925	$71.99	$72.00	$72.00
Purchase #3	$239.97	12.464%	$269.8799	$269.88	$269.90	$269.90
Purchase #4	$86.59	3.609%	$89.715	$89.72	$89.70	$89.70
Purchase #5	$75.92	4.401%	$79.2612	$79.26	$79.25	$79.30
Purchase #6	$200.92	9.438%	$219.8828	$219.88	$219.90	$219.90
Purchase #7	$144.41	6.128%	$153.2594	$153.26	$153.25	$153.30
7 purchase totals =	$956.30		$1,041.4336	$1,041.43	$1,041.45	$1,041.50