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	$245.75	6.303%	$261.2396	$261.24	$261.25	$261.20
Purchase #2	$203.60	3.590%	$210.9092	$210.91	$210.90	$210.90
Purchase #3	$179.81	3.367%	$185.8642	$185.86	$185.85	$185.90
Purchase #4	$92.72	12.678%	$104.475	$104.48	$104.50	$104.50
Purchase #5	$140.77	7.371%	$151.1462	$151.15	$151.15	$151.10
Purchase #6	$28.67	13.154%	$32.4413	$32.44	$32.45	$32.40
Purchase #7	$62.45	9.252%	$68.2279	$68.23	$68.25	$68.20
7 purchase totals =	$953.77		$1,014.3034	$1,014.31	$1,014.35	$1,014.20