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	$109.80	10.110%	$120.9008	$120.90	$120.90	$120.90
Purchase #2	$142.51	6.612%	$151.9328	$151.93	$151.95	$151.90
Purchase #3	$127.30	3.469%	$131.716	$131.72	$131.70	$131.70
Purchase #4	$215.59	13.452%	$244.5912	$244.59	$244.60	$244.60
Purchase #5	$249.37	9.500%	$273.0602	$273.06	$273.05	$273.10
Purchase #6	$174.62	4.736%	$182.89	$182.89	$182.90	$182.90
Purchase #7	$133.42	10.497%	$147.4251	$147.43	$147.45	$147.40
7 purchase totals =	$1,152.61		$1,252.5161	$1,252.52	$1,252.55	$1,252.50