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	$154.92	8.685%	$168.3748	$168.37	$168.35	$168.40
Purchase #2	$243.37	7.530%	$261.6958	$261.70	$261.70	$261.70
Purchase #3	$49.43	12.459%	$55.5885	$55.59	$55.60	$55.60
Purchase #4	$112.72	11.190%	$125.3334	$125.33	$125.35	$125.30
Purchase #5	$129.72	12.252%	$145.6133	$145.61	$145.60	$145.60
Purchase #6	$131.43	11.119%	$146.0437	$146.04	$146.05	$146.00
Purchase #7	$108.85	3.564%	$112.7294	$112.73	$112.75	$112.70
7 purchase totals =	$930.44		$1,015.3789	$1,015.37	$1,015.40	$1,015.30