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	$60.32	10.356%	$66.5667	$66.57	$66.55	$66.60
Purchase #2	$124.48	5.351%	$131.1409	$131.14	$131.15	$131.10
Purchase #3	$166.74	9.506%	$182.5903	$182.59	$182.60	$182.60
Purchase #4	$45.40	6.537%	$48.3678	$48.37	$48.35	$48.40
Purchase #5	$202.38	3.830%	$210.1312	$210.13	$210.15	$210.10
Purchase #6	$6.66	10.795%	$7.3789	$7.38	$7.40	$7.40
Purchase #7	$165.55	7.612%	$178.1517	$178.15	$178.15	$178.20
7 purchase totals =	$771.53		$824.3275	$824.33	$824.35	$824.40