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	$82.31	8.550%	$89.3475	$89.35	$89.35	$89.30
Purchase #2	$25.66	10.550%	$28.3671	$28.37	$28.35	$28.40
Purchase #3	$57.94	12.279%	$65.0545	$65.05	$65.05	$65.10
Purchase #4	$206.45	10.192%	$227.4914	$227.49	$227.50	$227.50
Purchase #5	$102.61	13.448%	$116.409	$116.41	$116.40	$116.40
Purchase #6	$31.96	5.867%	$33.8351	$33.84	$33.85	$33.80
Purchase #7	$200.42	10.289%	$221.0412	$221.04	$221.05	$221.00
7 purchase totals =	$707.35		$781.5458	$781.55	$781.55	$781.50