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	$238.77	9.384%	$261.1762	$261.18	$261.20	$261.20
Purchase #2	$163.67	12.861%	$184.7196	$184.72	$184.70	$184.70
Purchase #3	$210.50	6.269%	$223.6962	$223.70	$223.70	$223.70
Purchase #4	$48.75	10.336%	$53.7888	$53.79	$53.80	$53.80
Purchase #5	$154.52	12.820%	$174.3295	$174.33	$174.35	$174.30
Purchase #6	$126.64	12.172%	$142.0546	$142.05	$142.05	$142.10
Purchase #7	$89.87	11.175%	$99.913	$99.91	$99.90	$99.90
7 purchase totals =	$1,032.72		$1,139.6779	$1,139.68	$1,139.70	$1,139.70