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	$131.81	12.687%	$148.5327	$148.53	$148.55	$148.50
Purchase #2	$142.65	6.572%	$152.025	$152.03	$152.05	$152.00
Purchase #3	$222.58	7.557%	$239.4004	$239.40	$239.40	$239.40
Purchase #4	$149.88	9.805%	$164.5757	$164.58	$164.60	$164.60
Purchase #5	$136.91	6.700%	$146.083	$146.08	$146.10	$146.10
Purchase #6	$38.45	5.575%	$40.5936	$40.59	$40.60	$40.60
Purchase #7	$157.97	10.489%	$174.5395	$174.54	$174.55	$174.50
7 purchase totals =	$980.25		$1,065.7499	$1,065.75	$1,065.85	$1,065.70