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	$6.71	7.278%	$7.1984	$7.20	$7.20	$7.20
Purchase #2	$148.32	10.806%	$164.3475	$164.35	$164.35	$164.30
Purchase #3	$211.79	3.259%	$218.6922	$218.69	$218.70	$218.70
Purchase #4	$179.67	9.511%	$196.7584	$196.76	$196.75	$196.80
Purchase #5	$97.73	6.267%	$103.8547	$103.85	$103.85	$103.90
Purchase #6	$152.64	13.117%	$172.6618	$172.66	$172.65	$172.70
Purchase #7	$213.68	9.251%	$233.4475	$233.45	$233.45	$233.40
7 purchase totals =	$1,010.54		$1,096.9605	$1,096.96	$1,096.95	$1,097.00