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	$75.46	9.791%	$82.8483	$82.85	$82.85	$82.80
Purchase #2	$238.97	8.633%	$259.6003	$259.60	$259.60	$259.60
Purchase #3	$238.76	13.773%	$271.6444	$271.64	$271.65	$271.60
Purchase #4	$51.88	7.550%	$55.7969	$55.80	$55.80	$55.80
Purchase #5	$160.76	9.427%	$175.9148	$175.91	$175.90	$175.90
Purchase #6	$146.58	4.629%	$153.3652	$153.37	$153.35	$153.40
Purchase #7	$143.61	11.630%	$160.3118	$160.31	$160.30	$160.30
7 purchase totals =	$1,056.02		$1,159.4817	$1,159.48	$1,159.45	$1,159.40