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	$6.52	9.739%	$7.155	$7.16	$7.15	$7.20
Purchase #2	$177.30	3.151%	$182.8867	$182.89	$182.90	$182.90
Purchase #3	$174.89	12.205%	$196.2353	$196.24	$196.25	$196.20
Purchase #4	$191.62	3.281%	$197.9071	$197.91	$197.90	$197.90
Purchase #5	$101.32	12.204%	$113.6851	$113.69	$113.70	$113.70
Purchase #6	$104.59	5.526%	$110.3696	$110.37	$110.35	$110.40
Purchase #7	$123.96	10.868%	$137.432	$137.43	$137.45	$137.40
7 purchase totals =	$880.20		$945.6708	$945.69	$945.70	$945.70