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	$237.43	10.415%	$262.1583	$262.16	$262.15	$262.20
Purchase #2	$236.72	11.158%	$263.1332	$263.13	$263.15	$263.10
Purchase #3	$133.86	13.780%	$152.3059	$152.31	$152.30	$152.30
Purchase #4	$98.61	3.701%	$102.2596	$102.26	$102.25	$102.30
Purchase #5	$73.84	11.869%	$82.6041	$82.60	$82.60	$82.60
Purchase #6	$76.36	7.601%	$82.1641	$82.16	$82.15	$82.20
Purchase #7	$186.75	12.479%	$210.0545	$210.05	$210.05	$210.10
7 purchase totals =	$1,043.57		$1,154.6797	$1,154.67	$1,154.65	$1,154.80