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	$193.58	3.497%	$200.3495	$200.35	$200.35	$200.30
Purchase #2	$236.49	9.607%	$259.2096	$259.21	$259.20	$259.20
Purchase #3	$200.79	6.331%	$213.502	$213.50	$213.50	$213.50
Purchase #4	$112.79	3.276%	$116.485	$116.49	$116.50	$116.50
Purchase #5	$17.59	11.386%	$19.5928	$19.59	$19.60	$19.60
Purchase #6	$88.28	3.451%	$91.3265	$91.33	$91.35	$91.30
Purchase #7	$91.40	8.761%	$99.4076	$99.41	$99.40	$99.40
7 purchase totals =	$940.92		$999.8730	$999.88	$999.90	$999.80