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	$211.45	11.419%	$235.5955	$235.60	$235.60	$235.60
Purchase #2	$52.51	8.367%	$56.9035	$56.90	$56.90	$56.90
Purchase #3	$174.36	8.741%	$189.6008	$189.60	$189.60	$189.60
Purchase #4	$51.85	5.604%	$54.7557	$54.76	$54.75	$54.80
Purchase #5	$64.38	9.173%	$70.2856	$70.29	$70.30	$70.30
Purchase #6	$162.60	4.299%	$169.5902	$169.59	$169.60	$169.60
Purchase #7	$14.31	3.758%	$14.8478	$14.85	$14.85	$14.80
7 purchase totals =	$731.46		$791.5791	$791.59	$791.60	$791.60