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	$152.25	7.849%	$164.2001	$164.20	$164.20	$164.20
Purchase #2	$80.31	11.471%	$89.5224	$89.52	$89.50	$89.50
Purchase #3	$94.39	7.870%	$101.8185	$101.82	$101.80	$101.80
Purchase #4	$103.35	10.215%	$113.9072	$113.91	$113.90	$113.90
Purchase #5	$127.75	5.759%	$135.1071	$135.11	$135.10	$135.10
Purchase #6	$14.65	11.388%	$16.3183	$16.32	$16.30	$16.30
Purchase #7	$123.40	7.433%	$132.5723	$132.57	$132.55	$132.60
7 purchase totals =	$696.10		$753.4459	$753.45	$753.35	$753.40