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	$60.51	11.564%	$67.5074	$67.51	$67.50	$67.50
Purchase #2	$80.47	7.447%	$86.4626	$86.46	$86.45	$86.50
Purchase #3	$65.65	5.686%	$69.3829	$69.38	$69.40	$69.40
Purchase #4	$143.75	3.243%	$148.4118	$148.41	$148.40	$148.40
Purchase #5	$162.34	6.289%	$172.5496	$172.55	$172.55	$172.50
Purchase #6	$182.54	5.134%	$191.9116	$191.91	$191.90	$191.90
Purchase #7	$105.32	5.463%	$111.0736	$111.07	$111.05	$111.10
7 purchase totals =	$800.58		$847.2995	$847.29	$847.25	$847.30