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	$168.90	9.716%	$185.3103	$185.31	$185.30	$185.30
Purchase #2	$201.92	4.263%	$210.5278	$210.53	$210.55	$210.50
Purchase #3	$59.46	4.490%	$62.1298	$62.13	$62.15	$62.10
Purchase #4	$119.83	9.349%	$131.0329	$131.03	$131.05	$131.00
Purchase #5	$115.44	8.393%	$125.1289	$125.13	$125.15	$125.10
Purchase #6	$72.73	13.398%	$82.4744	$82.47	$82.45	$82.50
Purchase #7	$138.40	5.129%	$145.4985	$145.50	$145.50	$145.50
7 purchase totals =	$876.68		$942.1026	$942.10	$942.15	$942.00