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	$100.32	4.666%	$105.0009	$105.00	$105.00	$105.00
Purchase #2	$157.63	3.500%	$163.1471	$163.15	$163.15	$163.10
Purchase #3	$130.52	9.189%	$142.5135	$142.51	$142.50	$142.50
Purchase #4	$226.95	4.127%	$236.3162	$236.32	$236.30	$236.30
Purchase #5	$43.50	8.314%	$47.1166	$47.12	$47.10	$47.10
Purchase #6	$85.38	5.581%	$90.1451	$90.15	$90.15	$90.10
Purchase #7	$135.60	11.805%	$151.6076	$151.61	$151.60	$151.60
7 purchase totals =	$879.90		$935.8470	$935.86	$935.80	$935.70