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	$237.28	4.441%	$247.8176	$247.82	$247.80	$247.80
Purchase #2	$182.59	4.212%	$190.2807	$190.28	$190.30	$190.30
Purchase #3	$70.76	3.547%	$73.2699	$73.27	$73.25	$73.30
Purchase #4	$60.25	11.303%	$67.0601	$67.06	$67.05	$67.10
Purchase #5	$140.29	11.613%	$156.5819	$156.58	$156.60	$156.60
Purchase #6	$80.86	6.682%	$86.2631	$86.26	$86.25	$86.30
Purchase #7	$71.78	12.775%	$80.9499	$80.95	$80.95	$80.90
7 purchase totals =	$843.81		$902.2232	$902.22	$902.20	$902.30