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	$229.29	9.443%	$250.9419	$250.94	$250.95	$250.90
Purchase #2	$140.66	3.179%	$145.1316	$145.13	$145.15	$145.10
Purchase #3	$83.31	12.873%	$94.0345	$94.03	$94.05	$94.00
Purchase #4	$65.56	5.478%	$69.1514	$69.15	$69.15	$69.20
Purchase #5	$242.96	5.776%	$256.9934	$256.99	$257.00	$257.00
Purchase #6	$53.25	12.392%	$59.8487	$59.85	$59.85	$59.80
Purchase #7	$98.87	3.104%	$101.9389	$101.94	$101.95	$101.90
7 purchase totals =	$913.90		$978.0404	$978.03	$978.10	$977.90