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	$144.82	10.741%	$160.3751	$160.38	$160.40	$160.40
Purchase #2	$241.78	6.538%	$257.5876	$257.59	$257.60	$257.60
Purchase #3	$144.55	12.678%	$162.876	$162.88	$162.90	$162.90
Purchase #4	$93.45	6.282%	$99.3205	$99.32	$99.30	$99.30
Purchase #5	$181.95	6.365%	$193.5311	$193.53	$193.55	$193.50
Purchase #6	$74.45	12.289%	$83.5992	$83.60	$83.60	$83.60
Purchase #7	$74.74	9.394%	$81.7611	$81.76	$81.75	$81.80
7 purchase totals =	$955.74		$1,039.0506	$1,039.06	$1,039.10	$1,039.10