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	$204.75	4.238%	$213.4273	$213.43	$213.45	$213.40
Purchase #2	$178.96	13.186%	$202.5577	$202.56	$202.55	$202.60
Purchase #3	$155.31	13.679%	$176.5549	$176.55	$176.55	$176.60
Purchase #4	$72.79	13.278%	$82.4551	$82.46	$82.45	$82.50
Purchase #5	$238.91	10.712%	$264.502	$264.50	$264.50	$264.50
Purchase #6	$88.38	8.431%	$95.8313	$95.83	$95.85	$95.80
Purchase #7	$27.38	12.328%	$30.7554	$30.76	$30.75	$30.80
7 purchase totals =	$966.48		$1,066.0837	$1,066.09	$1,066.10	$1,066.20