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	$73.74	10.691%	$81.6235	$81.62	$81.60	$81.60
Purchase #2	$154.67	5.124%	$162.5953	$162.60	$162.60	$162.60
Purchase #3	$135.64	9.511%	$148.5407	$148.54	$148.55	$148.50
Purchase #4	$182.74	4.727%	$191.3781	$191.38	$191.40	$191.40
Purchase #5	$106.40	5.166%	$111.8966	$111.90	$111.90	$111.90
Purchase #6	$17.78	4.582%	$18.5947	$18.59	$18.60	$18.60
Purchase #7	$121.69	13.465%	$138.0756	$138.08	$138.10	$138.10
7 purchase totals =	$792.66		$852.7045	$852.71	$852.75	$852.70