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	$162.41	3.158%	$167.5389	$167.54	$167.55	$167.50
Purchase #2	$134.57	5.361%	$141.7843	$141.78	$141.80	$141.80
Purchase #3	$200.78	6.323%	$213.4753	$213.48	$213.50	$213.50
Purchase #4	$71.57	6.515%	$76.2328	$76.23	$76.25	$76.20
Purchase #5	$154.72	5.713%	$163.5592	$163.56	$163.55	$163.60
Purchase #6	$152.59	8.856%	$166.1034	$166.10	$166.10	$166.10
Purchase #7	$12.78	10.560%	$14.1296	$14.13	$14.15	$14.10
7 purchase totals =	$889.42		$942.8235	$942.82	$942.90	$942.80