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	$162.41	10.637%	$179.6856	$179.69	$179.70	$179.70
Purchase #2	$71.38	6.855%	$76.2731	$76.27	$76.25	$76.30
Purchase #3	$6.67	11.815%	$7.4581	$7.46	$7.45	$7.50
Purchase #4	$6.60	10.514%	$7.2939	$7.29	$7.30	$7.30
Purchase #5	$142.94	10.199%	$157.5185	$157.52	$157.50	$157.50
Purchase #6	$33.83	11.220%	$37.6257	$37.63	$37.65	$37.60
Purchase #7	$95.75	9.561%	$104.9047	$104.90	$104.90	$104.90
7 purchase totals =	$519.58		$570.7596	$570.76	$570.75	$570.80