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	$210.86	9.872%	$231.6761	$231.68	$231.70	$231.70
Purchase #2	$146.88	5.765%	$155.3476	$155.35	$155.35	$155.30
Purchase #3	$240.36	3.356%	$248.4265	$248.43	$248.45	$248.40
Purchase #4	$216.31	3.104%	$223.0243	$223.02	$223.00	$223.00
Purchase #5	$202.45	9.753%	$222.1949	$222.19	$222.20	$222.20
Purchase #6	$162.87	6.149%	$172.8849	$172.88	$172.90	$172.90
Purchase #7	$103.72	7.857%	$111.8693	$111.87	$111.85	$111.90
7 purchase totals =	$1,283.45		$1,365.4236	$1,365.42	$1,365.45	$1,365.40