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	$89.90	4.716%	$94.1397	$94.14	$94.15	$94.10
Purchase #2	$64.50	13.667%	$73.3152	$73.32	$73.30	$73.30
Purchase #3	$19.63	8.719%	$21.3415	$21.34	$21.35	$21.30
Purchase #4	$13.52	5.140%	$14.2149	$14.21	$14.20	$14.20
Purchase #5	$88.68	5.823%	$93.8438	$93.84	$93.85	$93.80
Purchase #6	$79.95	13.166%	$90.4762	$90.48	$90.50	$90.50
Purchase #7	$194.71	8.124%	$210.5282	$210.53	$210.55	$210.50
7 purchase totals =	$550.89		$597.8595	$597.86	$597.90	$597.70