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	$174.66	9.276%	$190.8615	$190.86	$190.85	$190.90
Purchase #2	$90.45	13.120%	$102.317	$102.32	$102.30	$102.30
Purchase #3	$54.60	7.760%	$58.837	$58.84	$58.85	$58.80
Purchase #4	$98.59	7.404%	$105.8896	$105.89	$105.90	$105.90
Purchase #5	$64.58	11.358%	$71.915	$71.92	$71.90	$71.90
Purchase #6	$247.89	13.166%	$280.5272	$280.53	$280.55	$280.50
Purchase #7	$147.84	10.293%	$163.0572	$163.06	$163.05	$163.10
7 purchase totals =	$878.61		$973.4045	$973.42	$973.40	$973.40