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	$41.61	7.269%	$44.6346	$44.63	$44.65	$44.60
Purchase #2	$32.53	7.276%	$34.8969	$34.90	$34.90	$34.90
Purchase #3	$40.26	6.119%	$42.7235	$42.72	$42.70	$42.70
Purchase #4	$154.34	9.149%	$168.4606	$168.46	$168.45	$168.50
Purchase #5	$38.46	5.160%	$40.4445	$40.44	$40.45	$40.40
Purchase #6	$188.79	6.849%	$201.7202	$201.72	$201.70	$201.70
Purchase #7	$245.82	7.388%	$263.9812	$263.98	$264.00	$264.00
7 purchase totals =	$741.81		$796.8615	$796.85	$796.85	$796.80