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	$82.63	4.306%	$86.188	$86.19	$86.20	$86.20
Purchase #2	$232.31	13.166%	$262.8959	$262.90	$262.90	$262.90
Purchase #3	$132.45	3.617%	$137.2407	$137.24	$137.25	$137.20
Purchase #4	$127.88	10.629%	$141.4724	$141.47	$141.45	$141.50
Purchase #5	$210.28	6.496%	$223.9398	$223.94	$223.95	$223.90
Purchase #6	$123.97	7.509%	$133.2789	$133.28	$133.30	$133.30
Purchase #7	$58.74	11.165%	$65.2983	$65.30	$65.30	$65.30
7 purchase totals =	$968.26		$1,050.3140	$1,050.32	$1,050.35	$1,050.30