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	$99.60	5.357%	$104.9356	$104.94	$104.95	$104.90
Purchase #2	$172.53	5.130%	$181.3808	$181.38	$181.40	$181.40
Purchase #3	$81.52	4.339%	$85.0572	$85.06	$85.05	$85.10
Purchase #4	$64.85	5.764%	$68.588	$68.59	$68.60	$68.60
Purchase #5	$184.72	3.714%	$191.5805	$191.58	$191.60	$191.60
Purchase #6	$55.74	6.302%	$59.2527	$59.25	$59.25	$59.30
Purchase #7	$171.94	13.712%	$195.5164	$195.52	$195.50	$195.50
7 purchase totals =	$830.90		$886.3112	$886.32	$886.35	$886.40