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	$65.39	3.765%	$67.8519	$67.85	$67.85	$67.90
Purchase #2	$209.82	13.568%	$238.2884	$238.29	$238.30	$238.30
Purchase #3	$210.68	6.458%	$224.2857	$224.29	$224.30	$224.30
Purchase #4	$93.53	3.125%	$96.4528	$96.45	$96.45	$96.50
Purchase #5	$163.64	5.661%	$172.9037	$172.90	$172.90	$172.90
Purchase #6	$61.88	4.382%	$64.5916	$64.59	$64.60	$64.60
Purchase #7	$67.58	6.695%	$72.1045	$72.10	$72.10	$72.10
7 purchase totals =	$872.52		$936.4786	$936.47	$936.50	$936.60