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	$68.27	3.126%	$70.4041	$70.40	$70.40	$70.40
Purchase #2	$83.54	12.822%	$94.2515	$94.25	$94.25	$94.30
Purchase #3	$106.97	4.460%	$111.7409	$111.74	$111.75	$111.70
Purchase #4	$98.54	12.655%	$111.0102	$111.01	$111.00	$111.00
Purchase #5	$132.73	7.569%	$142.7763	$142.78	$142.80	$142.80
Purchase #6	$109.62	12.439%	$123.2556	$123.26	$123.25	$123.30
Purchase #7	$36.69	13.240%	$41.5478	$41.55	$41.55	$41.50
7 purchase totals =	$636.36		$694.9864	$694.99	$695.00	$695.00