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	$159.45	8.250%	$172.6046	$172.60	$172.60	$172.60
Purchase #2	$125.74	6.458%	$133.8603	$133.86	$133.85	$133.90
Purchase #3	$247.89	11.833%	$277.2228	$277.22	$277.20	$277.20
Purchase #4	$240.97	8.527%	$261.5175	$261.52	$261.50	$261.50
Purchase #5	$70.77	4.148%	$73.7055	$73.71	$73.70	$73.70
Purchase #6	$226.25	5.154%	$237.9109	$237.91	$237.90	$237.90
Purchase #7	$41.27	6.262%	$43.8543	$43.85	$43.85	$43.90
7 purchase totals =	$1,112.34		$1,200.6759	$1,200.67	$1,200.60	$1,200.70