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	$130.78	4.297%	$136.3996	$136.40	$136.40	$136.40
Purchase #2	$145.33	10.609%	$160.7481	$160.75	$160.75	$160.70
Purchase #3	$28.83	10.604%	$31.8871	$31.89	$31.90	$31.90
Purchase #4	$60.93	4.823%	$63.8687	$63.87	$63.85	$63.90
Purchase #5	$156.83	9.327%	$171.4575	$171.46	$171.45	$171.50
Purchase #6	$150.87	5.428%	$159.0592	$159.06	$159.05	$159.10
Purchase #7	$68.91	10.865%	$76.3971	$76.40	$76.40	$76.40
7 purchase totals =	$742.48		$799.8173	$799.83	$799.80	$799.90