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	$85.39	10.129%	$94.0392	$94.04	$94.05	$94.00
Purchase #2	$79.88	3.239%	$82.4673	$82.47	$82.45	$82.50
Purchase #3	$93.96	5.765%	$99.3768	$99.38	$99.40	$99.40
Purchase #4	$242.94	4.165%	$253.0585	$253.06	$253.05	$253.10
Purchase #5	$77.45	6.848%	$82.7538	$82.75	$82.75	$82.80
Purchase #6	$134.35	6.136%	$142.5937	$142.59	$142.60	$142.60
Purchase #7	$81.77	9.390%	$89.4482	$89.45	$89.45	$89.40
7 purchase totals =	$795.74		$843.7375	$843.74	$843.75	$843.80